Content skill for computing the self-employed retirement contribution deduction for US sole proprietors and single-member LLCs disregarded for federal tax purposes. Covers tax year 2025 SEP-IRA, Solo 401(k), SIMPLE IRA, and traditional/Roth IRA options with SECURE 2.0 super catch-up provisions. H…
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Every figure is drawn from this Tax Guide and cited to its source.
Solo 401k 2025 402(g) elective deferral limit
$23,500IRS Notice 2024-80.
§415(c) 2025 total defined-contribution 415(c) limit
$70,000IRS Notice 2024-80.
IRA 2025 IRA limit
$7,000 (+$1,000 catch-up age 50+)IRS Notice 2024-80.
Roth S 2025 Roth IRA phase-out, Single/HoH
$150,000-$165,000IRS Notice 2024-80.
Solo 401(k) year-specific figures table for TY2025
| Figure | Value for TY2025 | Primary source | |---|---|---| | Employee elective deferral limit | $23,500 | Notice 2024-80; IRC §402(g)(1) | | Catch-up contribution (age 50-59, 64+) | $7,500 | Notice 2024-80; IRC §414(v)(2)(B)(i) | | Super catch-up contribution (age 60-63) | $11,250 | Notice 2024-80; IRC §414(v)(2)(E); SECURE 2.0 §109 | | Total annual additions limit (§415(c)) | $70,000 | Notice 2024-80; IRC §415(c)(1)(A) | | Total with catch-up (age 50-59, 64+) | $77,500 | $70,000 + $7,500 | | Total with super catch-up (age 60-63) | $81,250 | $70,000 + $11,250 | | Employer contribution rate (on compensation) | 25% of compensation | IRC §415(c)(1)(B); IRC §404(a)(8) | | Effective employer rate for sole props | 20% of net SE earnings | See Section 5 derivation |Section 3
SEP-IRA year-specific figures table for TY2025
| Figure | Value for TY2025 | Primary source | |---|---|---| | Maximum contribution | $70,000 | Notice 2024-80; IRC §415(c)(1)(A) | | Contribution rate (on compensation) | 25% of compensation | IRC §404(h)(1)(C) | | Effective rate for sole props | 20% of net SE earnings | See Section 5 derivation | | Compensation cap | $350,000 | Notice 2024-80; IRC §401(a)(17) |
Reviewed against the cited tax authorities by a licensed accountant on 2026-06-03. Items flagged for further clarification are tracked separately and excluded here. This block is generated from verified
skill_facts— edit the facts, not the prose.
This file is a content skill that loads on top of us-tax-workflow-base v0.1. It computes the deductible retirement contributions available to a sole proprietor or single-member LLC owner for tax year 2025. It does not classify transactions (that is us-sole-prop-bookkeeping), compute Schedule C net profit or SE tax (that is us-schedule-c-and-se-computation), or compute the QBI deduction (that is us-qbi-deduction, which consumes this skill's output).
Where this skill fits in the pipeline:
Bank statement / source data
↓
us-sole-prop-bookkeeping (classifies every transaction into a Schedule C line)
↓
us-schedule-c-and-se-computation (aggregates, computes net profit, computes SE tax)
↓
us-self-employed-retirement (THIS SKILL — computes retirement contribution deduction)
+ us-self-employed-health-insurance (companion — computes SE health insurance deduction)
↓
us-qbi-deduction (QBI deduction, adjusted for retirement and SE health insurance)
↓
us-quarterly-estimated-tax (safe harbor for following year)
Tax year coverage. This skill is current for tax year 2025 as of its currency date (April 2026). Contribution limits are from IRS Notice 2024-80 (November 2024). SECURE 2.0 Act provisions effective for 2025 are reflected, including the age 60-63 super catch-up.
The reviewer is the customer of this output. The skill produces a retirement contribution worksheet and a brief that the reviewing EA or CPA can audit and sign off on.
This skill covers, for tax year 2025:
This skill does NOT cover:
Tax year covered: 2025 (returns due April 15, 2026, or October 15, 2026 with extension).
Currency date: April 2026.
Legislation reflected:
Currency limitations:
Solo 401(k) year-specific figures table for TY2025 (Section 3)
| Figure | Value for TY2025 | Primary source |
|---|---|---|
| Employee elective deferral limit | $23,500 | Notice 2024-80; IRC §402(g)(1) |
| Catch-up contribution (age 50-59, 64+) | $7,500 | Notice 2024-80; IRC §414(v)(2)(B)(i) |
| Super catch-up contribution (age 60-63) | $11,250 | Notice 2024-80; IRC §414(v)(2)(E); SECURE 2.0 §109 |
| Total annual additions limit (§415(c)) | $70,000 | Notice 2024-80; IRC §415(c)(1)(A) |
| Total with catch-up (age 50-59, 64+) | $77,500 | $70,000 + $7,500 |
| Total with super catch-up (age 60-63) | $81,250 | $70,000 + $11,250 |
| Employer contribution rate (on compensation) | 25% of compensation | IRC §415(c)(1)(B); IRC §404(a)(8) |
| Effective employer rate for sole props | 20% of net SE earnings | See Section 5 derivation |
SEP-IRA year-specific figures table for TY2025 (Section 3)
| Figure | Value for TY2025 | Primary source |
|---|---|---|
| Maximum contribution | $70,000 | Notice 2024-80; IRC §415(c)(1)(A) |
| Contribution rate (on compensation) | 25% of compensation | IRC §404(h)(1)(C) |
| Effective rate for sole props | 20% of net SE earnings | See Section 5 derivation |
| Compensation cap | $350,000 | Notice 2024-80; IRC §401(a)(17) |
SIMPLE IRA year-specific figures table for TY2025 (Section 3)
| Figure | Value for TY2025 | Primary source |
|---|---|---|
| Employee deferral limit | $16,500 | Notice 2024-80; IRC §408(p)(2)(E) |
| Catch-up contribution (age 50-59, 64+) | $3,500 | Notice 2024-80; IRC §414(v)(2)(B)(ii) |
| Super catch-up contribution (age 60-63) | $5,250 | Notice 2024-80; IRC §414(v)(2)(E); SECURE 2.0 §109 |
| Employer match (dollar-for-dollar) | Up to 3% of compensation | IRC §408(p)(2)(A)(iii) |
| Employer non-elective alternative | 2% of compensation | IRC §408(p)(2)(B) |
| Compensation cap for 2% non-elective | $350,000 | Notice 2024-80; IRC §401(a)(17) |
Traditional and Roth IRA year-specific figures table for TY2025 (Section 3)
| Figure | Value for TY2025 | Primary source |
|---|---|---|
| IRA contribution limit | $7,000 | Notice 2024-80; IRC §219(b)(5)(A) |
| IRA catch-up (age 50+) | $1,000 | IRC §219(b)(5)(B); statutory, NOT indexed |
| Traditional IRA deductibility phase-out (single, covered by employer plan) | MAGI $79,000-$89,000 | Notice 2024-80; IRC §219(g)(3)(B)(i) |
| Traditional IRA deductibility phase-out (MFJ, covered by employer plan) | MAGI $126,000-$146,000 | Notice 2024-80; IRC §219(g)(3)(B)(i) |
| Traditional IRA deductibility phase-out (MFJ, not covered but spouse is) | MAGI $236,000-$246,000 | Notice 2024-80; IRC §219(g)(7) |
| Roth IRA contribution phase-out (single / HoH) | MAGI $150,000-$165,000 | Notice 2024-80; IRC §408A(c)(3) |
| Roth IRA contribution phase-out (MFJ) | MAGI $236,000-$246,000 | Notice 2024-80; IRC §408A(c)(3) |
| Roth IRA contribution phase-out (MFS) | MAGI $0-$10,000 | IRC §408A(c)(3)(C)(iii); statutory, not indexed |
For retirement contribution purposes, the sole proprietor's "compensation" is net self-employment earnings, defined as:
Net SE earnings = Schedule C net profit (Line 31)
× 92.35% [the §1402(a)(12) adjustment]
− Deductible half of SE tax [§164(f)]
Wait — that is not quite right. The computation is actually:
Step 1: Net SE income = Schedule C net profit × 92.35%
Step 2: SE tax = Net SE income × 15.3% (up to SS wage base) + 2.9% (Medicare on excess)
Step 3: Deductible half of SE tax = SE tax × 50%
Step 4: Net SE earnings for retirement = Schedule C net profit − Deductible half of SE tax
Why the difference matters: For retirement contribution purposes under IRC §401(c)(2), "earned income" of a self-employed individual is net earnings from self-employment reduced by:
When an employer contributes to an employee's SEP-IRA or 401(k) profit-sharing, the limit is 25% of the employee's compensation. But for a sole proprietor, the "compensation" is reduced by the contribution itself, creating circularity. The algebraic solution is shown above.
This is why the effective employer contribution rate for sole props is 20%, not 25%.
Net SE earnings for this formula = Schedule C net profit − deductible half of SE tax
Schedule C net profit: $100,000
× 92.35% (§1402(a)(12)): $92,350
SE tax (assuming all below SS wage base):
OASDI: $92,350 × 12.4% = $11,451
Medicare: $92,350 × 2.9% = $2,678
Total SE tax: $14,129
Deductible half: $7,065
Net SE earnings for retirement:
$100,000 − $7,065 = $92,935
Maximum employer contribution (SEP or Solo 401k profit-sharing):
20% × $92,935 = $18,587
Solo 401(k) with employee deferral:
Employee deferral (under age 50): $23,500
+ Employer (20% × $92,935): $18,587
Total: $42,087
(Under §415(c) $70,000 limit — OK)
The Solo 401(k) (also called individual 401(k) or one-participant 401(k)) is the most powerful retirement vehicle for sole props with no common-law employees. It combines:
Solo 401(k) contribution limits by age (Section 6)
| Age in 2025 | Employee deferral | Catch-up | Employer (max) | §415(c) cap | Maximum possible |
|---|---|---|---|---|---|
| Under 50 | $23,500 | $0 | 20% of net SE earnings, up to $46,500 | $70,000 | $70,000 |
| 50-59 | $23,500 | $7,500 | 20% of net SE earnings, up to $46,500 | $70,000 + $7,500 | $77,500 |
| 60-63 | $23,500 | $11,250 | 20% of net SE earnings, up to $46,500 | $70,000 + $11,250 | $81,250 |
| 64+ | $23,500 | $7,500 | 20% of net SE earnings, up to $46,500 | $70,000 + $7,500 | $77,500 |
Note on the §415(c) cap: The $70,000 limit applies to the sum of employee deferrals + employer contributions (NOT including catch-up). Catch-up contributions are above the §415(c) limit. So the true maximum is $70,000 + catch-up.
Note on the employer side cap: The employer contribution cannot exceed 20% of net SE earnings. The employee deferral + employer contribution (excluding catch-up) cannot exceed $70,000. These limits interact — whichever binds first controls.
Solo 401(k) establishment and contribution deadlines (Section 6)
| Action | Deadline |
|---|---|
| Establish a new Solo 401(k) plan | December 31, 2025 (for 2025 contributions) |
| Make employee elective deferrals (2025) | December 31, 2025 (must be made by end of tax year) |
| Make employer profit-sharing contributions (2025) | Tax filing deadline including extensions (April 15, 2026, or October 15, 2026 with extension) |
A SEP-IRA (Simplified Employee Pension) allows employer-only contributions. There is no employee deferral component. The maximum is 25% of compensation (20% effective for sole props), capped at $70,000 for 2025.
SEP-IRA establishment and contribution deadlines (Section 7)
| Action | Deadline |
|---|---|
| Establish SEP-IRA | Tax filing deadline including extensions (can establish and fund on same day) |
| Make 2025 contributions | Tax filing deadline including extensions (April 15, 2026, or October 15, 2026) |
A SIMPLE IRA (Savings Incentive Match Plan for Employees) is less common for solo practitioners but available. It allows both employee deferrals and employer contributions.
For the typical sole prop with no employees, the decision tree is:
Is net SE earnings > $0?
├── NO → No SE retirement contributions possible (may still contribute to IRA from other income)
├── YES → Continue
│
Was a Solo 401(k) established by Dec 31, 2025?
├── YES → Solo 401(k) is almost always the best choice
│ Employee deferral: up to $23,500
│ + Employer: 20% of net SE earnings
│ + Catch-up if applicable
│ + Optional Roth IRA on top ($7,000/$8,000 if MAGI permits)
│
├── NO → Can still establish a SEP-IRA by filing deadline
│ SEP-IRA: 20% of net SE earnings (max $70,000)
│ + Optional Roth IRA on top ($7,000/$8,000 if MAGI permits)
│
└── Income too low for meaningful employer contribution?
Consider traditional IRA ($7,000/$8,000) or Roth IRA
May be the only practical option if net SE earnings < $15,000
Conservative defaults table
| Ambiguity | Conservative default |
|---|---|
| Plan type not specified | Assume Solo 401(k) if established by Dec 31; otherwise SEP-IRA |
| Age not provided | Assume under 50 (lowest contribution limits); ask for age |
| Solo 401(k) establishment date unclear | Assume NOT established by Dec 31 (cannot use Solo 401(k)); default to SEP-IRA |
| Roth vs. traditional deferral preference not stated | Assume pre-tax (traditional) for maximum current-year deduction and QBI reduction |
| MAGI not computed for Roth eligibility | Compute MAGI from available data; if MAGI unclear, assume above Roth limits (no Roth recommendation) |
| Whether taxpayer has existing IRA balances (for backdoor Roth) | Assume yes (pro-rata rule applies); flag for reviewer |
| Plan contribution amount not specified | Compute maximum allowable; present maximum and let reviewer/taxpayer decide |
| SIMPLE IRA vs. other plans | Do NOT default to SIMPLE; it is inferior for most sole props without employees |
Reviewer attention thresholds
| Threshold | Trigger | Rationale |
|---|---|---|
| Total retirement contributions > $50,000 | Always flag | Verify §415(c) limit compliance |
| Solo 401(k) established after Oct 1 | Always flag | Verify December 31 establishment was completed |
| Sole prop has employees | Always flag | Nondiscrimination and coverage rules apply |
| Net SE earnings < $23,500 | Always flag | Employee deferral limited to net SE earnings; verify computation |
| Taxpayer age 60-63 | Always flag | Super catch-up eligible — verify age documentation |
| Multiple retirement plans in same year | Always flag | Aggregation rules and limits coordination required |
| Backdoor Roth flagged | Always flag | Pro-rata rule; verify no existing pre-tax IRA balances |
| MAGI near Roth or IRA deductibility phase-out | Always flag | Small income changes could affect eligibility |
| Solo 401(k) assets > $200,000 | Always flag | Form 5500-EZ filing requirement approaching or triggered |
Taxpayer: Maria Hernandez, single, age 34, freelance UX designer, net SE earnings = $62,644 (from Schedule C), deductible half of SE tax = $4,427. Solo 401(k) established December 2024.
Net SE earnings for retirement = $62,644 − $4,427 = $58,217
Employee deferral: $23,500 (under §402(g) limit)
Employer contribution: 20% × $58,217 = $11,643
Total: $35,143
§415(c) check: $23,500 + $11,643 = $35,143 ≤ $70,000 ✓
Deduction on Schedule 1: $35,143
Taxpayer: James Chen, single, age 42, freelance software developer, Schedule C net profit = $250,000, deductible half of SE tax = $16,583. No Solo 401(k) established (missed Dec 31 deadline).
Net SE earnings for retirement = $250,000 − $16,583 = $233,417
SEP-IRA: 20% × $233,417 = $46,683
§415(c) check: $46,683 ≤ $70,000 ✓
Deduction on Schedule 1: $46,683
Had he established a Solo 401(k):
Employee deferral: $23,500
Employer: $46,683 (same as SEP)
Total: $70,000 (hits §415(c) cap, so capped at $70,000)
Additional savings: $70,000 − $46,683 = $23,317 more in retirement
Taxpayer: Lisa Park, MFJ, age 61, freelance accountant, Schedule C net profit = $180,000, deductible half of SE tax = $12,717. Solo 401(k) established 2020.
Net SE earnings = $180,000 − $12,717 = $167,283
Employee deferral: $23,500
Super catch-up (age 60-63): $11,250
Employer: 20% × $167,283 = $33,457
Total: $68,207
§415(c) check: $23,500 + $33,457 = $56,957 ≤ $70,000 ✓
(catch-up is excluded from §415(c))
Total with catch-up: $56,957 + $11,250 = $68,207
Deduction on Schedule 1: $68,207
Taxpayer: Alex Rivera, single, age 28, freelance graphic designer, Schedule C net profit = $18,000, deductible half of SE tax = $1,272. No employer plan established.
Net SE earnings = $18,000 − $1,272 = $16,728
Could establish SEP-IRA by filing deadline:
20% × $16,728 = $3,346
Could establish Solo 401(k) by Dec 31:
Employee deferral: $16,728 (limited to net SE earnings)
Employer: $3,346
Total: limited by net SE earnings interaction
In practice: can defer up to $16,728 (less than $23,500 limit)
+ employer: 20% × $16,728 = $3,346
Total: up to ~$16,728 (deferral cannot exceed earned income)
Traditional IRA (no employer plan, fully deductible): $7,000
Roth IRA: $7,000 (MAGI well below $150,000)
Input: Schedule C net profit $100,000; deductible half SE tax $7,065; age 40; Solo 401(k) established. Expected: Net SE earnings for retirement = $92,935. Employee deferral = $23,500. Employer = 20% × $92,935 = $18,587. Total = $42,087. §415(c) check: $42,087 ≤ $70,000. Deduction = $42,087.
Input: Schedule C net profit $400,000; deductible half SE tax $23,886; age 55; no Solo 401(k). Expected: Net SE earnings = $376,114. SEP = 20% × $376,114 = $75,223, CAPPED at $70,000. SEP deduction = $70,000.
Input: Schedule C net profit $200,000; deductible half SE tax $14,130; age 62; Solo 401(k) established. Expected: Net SE earnings = $185,870. Employee deferral = $23,500. Employer = 20% × $185,870 = $37,174. Subtotal = $60,674 ≤ $70,000 §415(c). Super catch-up = $11,250. Total deduction = $71,924.
Input: Schedule C net profit $20,000; deductible half SE tax $1,413; age 30; Solo 401(k) established. Expected: Net SE earnings = $18,587. Employee deferral = $18,587 (limited by net SE earnings, not $23,500). Employer = 20% × $18,587 = $3,717. Total = $22,304. But total cannot exceed net SE earnings in a meaningful way — verify: $23,500 deferral limit > $18,587 net SE earnings, so deferral capped at $18,587. Total deduction = $22,304.
Input: Schedule C net profit $80,000; deductible half SE tax $5,652; age 45; Solo 401(k) established; also has W-2 job where deferred $15,000 in employer 401(k). Expected: Remaining Solo 401(k) deferral = $23,500 − $15,000 = $8,500. Net SE earnings = $74,348. Employer = 20% × $74,348 = $14,870. Solo 401(k) total = $8,500 + $14,870 = $23,370. (Employer contributions are separate from the shared deferral limit.)
Input: Schedule C net profit $120,000; SEP-IRA contribution $20,000; single; MAGI = $100,000 (after SE tax deduction); age 35. Expected: Active participant in SEP-IRA. Single phase-out: $79,000-$89,000. MAGI $100,000 > $89,000. Traditional IRA contribution is NOT deductible (but can still contribute nondeductibly or to Roth if MAGI < $150,000).
Upstream skill data consumed
| Upstream skill | Data consumed |
|---|---|
us-schedule-c-and-se-computation | Schedule C net profit (Line 31), deductible half of SE tax |
Downstream skill data provided
| Downstream skill | Data provided |
|---|---|
us-qbi-deduction | Deductible retirement contribution amount (reduces QBI) |
us-quarterly-estimated-tax | Retirement deduction amount (reduces estimated tax liability) |
us-federal-return-assembly | Retirement deduction for Schedule 1 Line 16 |
us-ca-return-assembly | Retirement deduction for federal return portion |
This skill and its outputs are provided for informational and computational purposes only and do not constitute tax, legal, or financial advice. Open Accountants and its contributors accept no liability for any errors, omissions, or outcomes arising from the use of this skill. All outputs must be reviewed and signed off by a qualified professional (such as a CPA, EA, tax attorney, or equivalent licensed practitioner in your jurisdiction) before filing or acting upon.
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Review status
Accountant-reviewed
Reviewed by a named licensed practitioner against the stated sources, as general reference material.
Other US Federal computations in the OpenAccountants Tax Library.
SIMPLE IRA year-specific figures table for TY2025
| Figure | Value for TY2025 | Primary source | |---|---|---| | Employee deferral limit | $16,500 | Notice 2024-80; IRC §408(p)(2)(E) | | Catch-up contribution (age 50-59, 64+) | $3,500 | Notice 2024-80; IRC §414(v)(2)(B)(ii) | | Super catch-up contribution (age 60-63) | $5,250 | Notice 2024-80; IRC §414(v)(2)(E); SECURE 2.0 §109 | | Employer match (dollar-for-dollar) | Up to 3% of compensation | IRC §408(p)(2)(A)(iii) | | Employer non-elective alternative | 2% of compensation | IRC §408(p)(2)(B) | | Compensation cap for 2% non-elective | $350,000 | Notice 2024-80; IRC §401(a)(17) |Section 3
Traditional and Roth IRA year-specific figures table for TY2025
| Figure | Value for TY2025 | Primary source | |---|---|---| | IRA contribution limit | $7,000 | Notice 2024-80; IRC §219(b)(5)(A) | | IRA catch-up (age 50+) | $1,000 | IRC §219(b)(5)(B); statutory, NOT indexed | | Traditional IRA deductibility phase-out (single, covered by employer plan) | MAGI $79,000-$89,000 | Notice 2024-80; IRC §219(g)(3)(B)(i) | | Traditional IRA deductibility phase-out (MFJ, covered by employer plan) | MAGI $126,000-$146,000 | Notice 2024-80; IRC §219(g)(3)(B)(i) | | Traditional IRA deductibility phase-out (MFJ, not covered but spouse is) | MAGI $236,000-$246,000 | Notice 2024-80; IRC §219(g)(7) | | Roth IRA contribution phase-out (single / HoH) | MAGI $150,000-$165,000 | Notice 2024-80; IRC §408A(c)(3) | | Roth IRA contribution phase-out (MFJ) | MAGI $236,000-$246,000 | Notice 2024-80; IRC §408A(c)(3) | | Roth IRA contribution phase-out (MFS) | MAGI $0-$10,000 | IRC §408A(c)(3)(C)(iii); statutory, not indexed |Section 3
Effective employer contribution rate derivation
Contribution = Rate × (Net SE earnings − Contribution) Contribution = Rate × Net SE earnings / (1 + Rate) At a 25% rate: Contribution = 0.25 / 1.25 × Net SE earnings = 20% of net SE earningsSee Section 5 derivation
Solo 401(k) contribution limits by age
| Age in 2025 | Employee deferral | Catch-up | Employer (max) | §415(c) cap | Maximum possible | |---|---|---|---|---|---| | Under 50 | $23,500 | $0 | 20% of net SE earnings, up to $46,500 | $70,000 | $70,000 | | 50-59 | $23,500 | $7,500 | 20% of net SE earnings, up to $46,500 | $70,000 + $7,500 | $77,500 | | 60-63 | $23,500 | $11,250 | 20% of net SE earnings, up to $46,500 | $70,000 + $11,250 | $81,250 | | 64+ | $23,500 | $7,500 | 20% of net SE earnings, up to $46,500 | $70,000 + $7,500 | $77,500 |Section 6
Roth elective deferrals rules
Roth deferrals: Count against the $23,500 elective deferral limit (same as pre-tax); Do NOT reduce current-year taxable income (no deduction); Do NOT reduce QBI (since there is no deduction); Grow tax-free and are distributed tax-free in retirement (if qualified). The skill computes Roth deferrals at $0 deduction but notes the total contributed for informational purposes. The employer profit-sharing portion is always pre-tax (traditional).Solo 401(k) plans can be designed to accept Roth (after-tax) elective deferrals
Solo 401(k) establishment and contribution deadlines
| Action | Deadline | |---|---| | Establish a new Solo 401(k) plan | December 31, 2025 (for 2025 contributions) | | Make employee elective deferrals (2025) | December 31, 2025 (must be made by end of tax year) | | Make employer profit-sharing contributions (2025) | Tax filing deadline including extensions (April 15, 2026, or October 15, 2026 with extension) |Section 6
Solo 401(k) December 31 establishment requirement
A Solo 401(k) must be established (plan adoption agreement executed) by December 31 of the tax year. If the plan was not established by December 31, 2025, the sole prop CANNOT make 2025 Solo 401(k) contributions — even if they file an extension. This is different from a SEP-IRA.Section 6
Form 5500-EZ filing requirement
If the Solo 401(k) plan assets exceed $250,000 at the end of the plan year, the sole prop must file Form 5500-EZ with the IRS. This is an annual filing, due by the last day of the 7th month after the plan year ends (July 31 for calendar-year plans). Failure to file triggers a $250/day penalty (up to $150,000). The skill flags this requirement when estimated plan assets exceed $200,000.Section 6
Maximum SEP contribution formula
Maximum SEP contribution = lesser of: (a) 20% × (Schedule C net profit − deductible half of SE tax) (b) $70,000Section 7
SEP-IRA establishment and contribution deadlines
| Action | Deadline | |---|---| | Establish SEP-IRA | Tax filing deadline including extensions (can establish and fund on same day) | | Make 2025 contributions | Tax filing deadline including extensions (April 15, 2026, or October 15, 2026) |Section 7
SEP-IRA key advantage
A sole prop who did not plan ahead can establish a SEP-IRA and make 2025 contributions as late as October 15, 2026 (if they file an extension). This is NOT possible with a Solo 401(k).Section 7
SIMPLE IRA contribution formula
Employee deferral: up to $16,500 (2025) Catch-up (age 50-59, 64+): additional $3,500 Super catch-up (age 60-63): additional $5,250 Employer match: dollar-for-dollar up to 3% of net SE earnings OR Employer non-elective: 2% of net SE earnings (up to $350,000 comp cap = max $7,000)Section 8
SIMPLE IRA restriction and comparison
Almost never for a sole prop. The SIMPLE IRA has lower deferral limits ($16,500 vs. $23,500) and lower employer contribution potential. It exists primarily for small businesses with employees who want a simpler alternative to a 401(k). **The SIMPLE IRA has a critical restriction:** If a sole prop maintains a SIMPLE IRA, they generally cannot also maintain a Solo 401(k) or SEP-IRA for the same year. The SIMPLE IRA must be the only employer plan.Section 8
SIMPLE IRA establishment deadline
A SIMPLE IRA must be established by October 1 of the tax year (e.g., October 1, 2025 for 2025 contributions). For a new business, it must be established as soon as administratively feasible but no later than October 1 if the business started before October 1.Section 8
Traditional IRA contribution limits (2025)
Under age 50: $7,000; Age 50+: $8,000 ($7,000 + $1,000 catch-up)Section 9
Traditional IRA deductibility phase-out rules
A sole prop who participates in a Solo 401(k), SEP-IRA, or SIMPLE IRA is considered an "active participant" in an employer plan. This triggers the deductibility phase-out for traditional IRA contributions: **Single / Head of Household (active participant):** - MAGI ≤ $79,000: fully deductible - $79,000 < MAGI < $89,000: partially deductible (pro-rata) - MAGI ≥ $89,000: not deductible (but can still contribute — nondeductible contribution tracked on Form 8606) **Married Filing Jointly (active participant):** - MAGI ≤ $126,000: fully deductible - $126,000 < MAGI < $146,000: partially deductible - MAGI ≥ $146,000: not deductible **MFJ (NOT active participant, but spouse IS):** - MAGI ≤ $236,000: fully deductible - $236,000 < MAGI < $246,000: partially deductible - MAGI ≥ $246,000: not deductible **If the sole prop does NOT have any employer plan (no SEP, no Solo 401(k), no SIMPLE):** The traditional IRA contribution is fully deductible regardless of income. However, this scenario is unlikely — the sole prop is leaving significant tax savings on the table by not having a plan.Section 9
Traditional IRA contribution deadline
Traditional IRA contributions for 2025 are due by April 15, 2026 (the tax filing deadline WITHOUT extensions). Extensions do not extend the IRA contribution deadline.Section 9
Traditional IRA interaction with other plans
A traditional IRA contribution is IN ADDITION to Solo 401(k) or SEP-IRA contributions. They use different limits and different IRC sections. But the deductibility phase-out kicks in when the taxpayer is an active participant in another plan.Section 9
Roth IRA contribution limits (2025)
Same as traditional IRA: $7,000 ($8,000 if age 50+). The combined traditional + Roth IRA contribution cannot exceed $7,000 ($8,000 if 50+).Section 10
Roth IRA income limits
**Single / Head of Household:** - MAGI < $150,000: full contribution allowed - $150,000 ≤ MAGI < $165,000: reduced contribution (pro-rata phase-out) - MAGI ≥ $165,000: $0 direct Roth IRA contribution **Married Filing Jointly:** - MAGI < $236,000: full contribution allowed - $236,000 ≤ MAGI < $246,000: reduced contribution - MAGI ≥ $246,000: $0 direct Roth IRA contribution **Married Filing Separately:** - MAGI < $10,000: reduced contribution - MAGI ≥ $10,000: $0Section 10
Backdoor Roth IRA strategy
High-income sole props who exceed the Roth IRA income limits can use the "backdoor" strategy: 1. Make a nondeductible traditional IRA contribution ($7,000/$8,000) 2. Convert to Roth IRA (Roth conversion — taxable on any pre-tax amounts) **The skill flags this strategy when MAGI exceeds Roth limits but does NOT compute the conversion mechanics.** The pro-rata rule under §408(d)(2) (aggregation of all traditional IRA balances) makes backdoor Roth conversions complex when the taxpayer has existing pre-tax IRA balances. Refer to reviewer.§408(d)(2)
Roth IRA and QBI
Roth IRA contributions are after-tax. They are not deductible and do not appear on Schedule 1. They do NOT reduce QBI.Section 10
Roth IRA contribution deadline
Same as traditional IRA: April 15, 2026 (no extension). This applies to both regular and catch-up contributions.Section 10
Crossover point formula
Solo 401(k) total = $23,500 (deferral) + 20% × net SE earnings (employer) SEP-IRA total = 20% × net SE earnings Solo 401(k) > SEP-IRA when net SE earnings < $117,500 (because the $23,500 deferral advantage is only overcome when 20% × net SE earnings exceeds the deferral limit, and the combined Solo 401(k) is capped at $70,000 anyway) At net SE earnings of ~$232,500: both Solo 401(k) employer + deferral and SEP-IRA hit the $70,000 cap ($232,500 × 20% = $46,500 employer + $23,500 deferral = $70,000). Above that, the Solo 401(k) catch-up provides the only additional room.Section 11
Conservative defaults table
| Ambiguity | Conservative default | |---|---| | Plan type not specified | Assume Solo 401(k) if established by Dec 31; otherwise SEP-IRA | | Age not provided | Assume under 50 (lowest contribution limits); ask for age | | Solo 401(k) establishment date unclear | Assume NOT established by Dec 31 (cannot use Solo 401(k)); default to SEP-IRA | | Roth vs. traditional deferral preference not stated | Assume pre-tax (traditional) for maximum current-year deduction and QBI reduction | | MAGI not computed for Roth eligibility | Compute MAGI from available data; if MAGI unclear, assume above Roth limits (no Roth recommendation) | | Whether taxpayer has existing IRA balances (for backdoor Roth) | Assume yes (pro-rata rule applies); flag for reviewer | | Plan contribution amount not specified | Compute maximum allowable; present maximum and let reviewer/taxpayer decide | | SIMPLE IRA vs. other plans | Do NOT default to SIMPLE; it is inferior for most sole props without employees |
R-RET-DB — Defined benefit plan inquiry
Trigger: Taxpayer asks about a defined benefit plan, cash balance plan, or pension. Output: "Defined benefit plans require actuarial computation, Form 5500 filing, and ongoing plan administration that is beyond the scope of this skill. These plans can allow contributions substantially exceeding the §415(c) limit and are worth exploring for high-income sole props ($300K+ net SE earnings). Please consult an actuary or retirement plan specialist."
R-RET-EMPLOYEES — Sole prop has common-law employees
Trigger: The taxpayer has employees (pays W-2 wages), which triggers nondiscrimination, top-heavy, and coverage rules for 401(k) and SEP plans. Output: "When a sole prop has common-law employees, retirement plan contributions for the owner must satisfy nondiscrimination and coverage rules under §401(a)(4) and §410(b). This skill covers one-participant (solo) plans only. Please consult a retirement plan administrator or CPA."
R-RET-EXCESS — Excess contributions
Trigger: Taxpayer may have contributed more than the limit. Output: "Excess contributions to retirement plans are subject to a 6% excise tax under §4973 (IRAs) or must be corrected under the plan's terms (401(k)/SEP). This skill does not compute excess contribution penalties. Please consult a CPA or tax attorney."
R-RET-RMD — Required minimum distributions
Trigger: Taxpayer is age 73+ and has retirement accounts. Output: "Required minimum distributions under §401(a)(9) must begin by April 1 following the year the taxpayer turns 73 (under SECURE 2.0 schedule). RMD computation is out of scope. Please consult a CPA or financial advisor."
R-RET-ROTHCONV — Roth conversion strategy
Trigger: Taxpayer asks about converting traditional IRA or 401(k) to Roth. Output: "Roth conversions are taxable events with complex interactions (pro-rata rule, state tax, impact on ACA subsidies, Medicare IRMAA). This skill flags the backdoor Roth strategy but does not compute conversion mechanics. Please consult a CPA or financial advisor."
Reviewer attention thresholds
| Threshold | Trigger | Rationale | |---|---|---| | Total retirement contributions > $50,000 | Always flag | Verify §415(c) limit compliance | | Solo 401(k) established after Oct 1 | Always flag | Verify December 31 establishment was completed | | Sole prop has employees | Always flag | Nondiscrimination and coverage rules apply | | Net SE earnings < $23,500 | Always flag | Employee deferral limited to net SE earnings; verify computation | | Taxpayer age 60-63 | Always flag | Super catch-up eligible — verify age documentation | | Multiple retirement plans in same year | Always flag | Aggregation rules and limits coordination required | | Backdoor Roth flagged | Always flag | Pro-rata rule; verify no existing pre-tax IRA balances | | MAGI near Roth or IRA deductibility phase-out | Always flag | Small income changes could affect eligibility | | Solo 401(k) assets > $200,000 | Always flag | Form 5500-EZ filing requirement approaching or triggered |
Edge case 1 — Net SE earnings negative
Net SE earnings are negative (Schedule C loss). No SE retirement contributions allowed. May still contribute to a traditional or Roth IRA using earned income from other sources (W-2 wages).
Edge case 2 — Employee deferral exceeds net SE earnings
The elective deferral cannot exceed net SE earnings from the business. If net SE earnings are $15,000, the maximum deferral is $15,000, not $23,500.
Edge case 3 — Multiple self-employment activities
If the taxpayer has multiple Schedule Cs, net SE earnings are aggregated. A loss from one business reduces net SE earnings available for retirement contributions from another.
Edge case 4 — Part-year self-employment
No pro-ration of limits. If the taxpayer was self-employed for 3 months and earned $20,000, the full $23,500 deferral limit applies (subject to net SE earnings limitation).
Edge case 5 — Taxpayer also has W-2 income with employer 401(k)
The $23,500 elective deferral limit is SHARED across all 401(k) plans (including employer 401(k) and Solo 401(k)). If the taxpayer deferred $20,000 at their employer, only $3,500 remains for Solo 401(k) deferral. Employer contributions are NOT shared — each plan has its own §415(c) limit.
Edge case 6 — Age 60-63 super catch-up not available for SEP-IRA
The super catch-up applies to elective deferrals only (401(k), SIMPLE). SEP-IRA has no deferral component and therefore no catch-up.
Edge case 7 — SIMPLE IRA 2-year rule
If the taxpayer previously had a SIMPLE IRA and is within the 2-year period from the first SIMPLE contribution, rollovers to a traditional IRA or 401(k) are restricted. The 25% early withdrawal penalty (instead of the normal 10%) applies during this period.
Edge case 8 — Spousal IRA
A self-employed taxpayer filing MFJ can fund a spousal IRA ($7,000/$8,000) for a non-working or low-earning spouse, even though the spouse has no earned income of their own, as long as the combined earned income exceeds the total IRA contributions.
Edge case 9 — Contribution deadline with extension
Solo 401(k) employer contributions and SEP-IRA contributions can be made up to October 15, 2026 if the taxpayer files an extension. The extension must actually be filed — the contribution deadline is the actual filing deadline, not an automatic grace period.
Edge case 10 — Roth Solo 401(k) deferrals do not reduce QBI
Pre-tax (traditional) Solo 401(k) deferrals reduce QBI via the Schedule 1 deduction. Roth deferrals do not reduce QBI because they are not deductible. This affects the downstream QBI computation.
Prohibition 1 — Employer contribution rate
NEVER use the 25% rate directly for a sole prop's employer contribution. The effective rate is 20% (25% / 1.25) because the contribution reduces the base. Using 25% overstates the maximum contribution.
Prohibition 2 — Solo 401(k) establishment deadline
NEVER allow a Solo 401(k) for 2025 if the plan was not established by December 31, 2025. Default to SEP-IRA if the establishment date is unknown or after December 31.
Prohibition 3 — §415(c) cap
NEVER ignore the §415(c) $70,000 cap. Employee deferrals + employer contributions (excluding catch-up) cannot exceed $70,000. Catch-up is on top.
Prohibition 4 — Super catch-up age restriction
NEVER apply the super catch-up to ages outside 60-63. Ages 50-59 and 64+ get the regular $7,500 catch-up. Only ages 60-63 get the $11,250 super catch-up.
Prohibition 5 — SIMPLE IRA recommendation
NEVER recommend a SIMPLE IRA over a Solo 401(k) for a sole prop without employees. SIMPLE IRA has lower limits and more restrictions. It is virtually always inferior for the target demographic.
Prohibition 6 — Shared deferral limit
NEVER forget that the $23,500 deferral limit is SHARED across all 401(k) plans. A taxpayer with both an employer 401(k) and a Solo 401(k) shares the limit.
Prohibition 7 — Deferral cannot exceed net SE earnings
NEVER allow employee deferrals to exceed net SE earnings. The deferral is capped at the lesser of $23,500 or net SE earnings.
Prohibition 8 — Compute deductible half of SE tax first
NEVER compute retirement contributions without first computing the deductible half of SE tax. The deductible half of SE tax reduces net SE earnings, which is the base for employer contributions.
Prohibition 9 — IRA contribution deadline
NEVER extend the IRA contribution deadline beyond April 15. Filing extensions do NOT extend the IRA contribution deadline. Only Solo 401(k) employer contributions and SEP-IRA contributions get the extension benefit.
Prohibition 10 — Roth contributions and QBI
NEVER treat Roth contributions (IRA or Solo 401(k) Roth deferral) as reducing QBI. Only deductible (pre-tax) contributions reduce QBI.
Upstream skill data consumed
| Upstream skill | Data consumed | |---|---| | `us-schedule-c-and-se-computation` | Schedule C net profit (Line 31), deductible half of SE tax |
Downstream skill data provided
| Downstream skill | Data provided | |---|---| | `us-qbi-deduction` | Deductible retirement contribution amount (reduces QBI) | | `us-quarterly-estimated-tax` | Retirement deduction amount (reduces estimated tax liability) | | `us-federal-return-assembly` | Retirement deduction for Schedule 1 Line 16 | | `us-ca-return-assembly` | Retirement deduction for federal return portion |
Rendered from the canonical facts model · facts last reviewed Jun 3, 2026. General reference only — confirm with a qualified professional before acting.
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