Colorado Self-Employed — Schedule C, Form DR 0104 & Estimated Payments

Confirm the taxpayer's legal structure (sole proprietor, single-member LLC, or multi-member partnership) and Colorado residency status. Determine whether any federal S-corp or partnership elections affect the return. Establish the tax year and whether this is a first-year filing that requires estimated-payment catch-up.

Aggregate all self-employment gross receipts from 1099-NEC, 1099-K, direct invoices, and cash income. Map deductible business expenses to Schedule C Part II categories. Compute net profit or loss, which drives both federal SE tax and Colorado starting income.

Compute self-employment tax on Schedule SE (15.3% on net earnings up to the Social Security wage base of $176,100 for 2025, then 2.9% Medicare above that). Take the 50% SE tax deduction and, if applicable, the self-employed health insurance deduction and SEP-IRA or Solo 401(k) contribution deduction above the line. Calculate the §199A qualified business income (QBI) deduction — it flows through federal taxable income and directly reduces Colorado starting income since Colorado conforms to federal taxable income (DR 0104 Line 1).

Start from federal taxable income (Form 1040 Line 15) and apply Colorado additions and subtractions on Schedule DR 0104AD. Apply the flat 4.4% Colorado rate. Identify applicable Colorado-specific credits (child care, enterprise zone, low-income taxpayer credit). Determine whether part-year or nonresident apportionment is needed (DR 0104PN).

Reconcile any DR 0104EP quarterly estimated payments made during the year against the Colorado tax liability. Assess underpayment penalty exposure using Colorado's annualized income installment method if income was uneven. Plan the Q4 payment or extension payment needed to meet the April 15 balance-due deadline. Colorado's safe harbor mirrors the federal rule: pay 100% of prior-year Colorado tax or 70% of current-year tax to avoid the penalty.

For self-employed taxpayers selling goods or taxable services, screen for Colorado sales-tax registration obligations (DR 0100 via SUTS) and the Retail Delivery Fee (DR 1786). Colorado's Wayfair economic nexus threshold is $100,000 in Colorado retail sales. The state sales-tax rate is 2.9% plus local; combined rates in metro areas typically run 7–9%. Self-employed service providers are generally exempt at the state level but must verify home-rule city rules for services.