Deadline Engine

What this file is

Obligation category: INTEL (Intelligence / Cross-cutting) Functional role: Calendar generation, deadline tracking, penalty estimation Status: Active

This is an intelligence skill that loads on top of workflow-base. Unlike content skills that compute a single obligation, this skill reads the user's full obligation profile and produces a consolidated filing calendar.

The reviewer is the customer of this output. The calendar and penalty estimates are working aids for a credentialed reviewer, not direct advice to the taxpayer.

Disclaimer. This skill provides deadline information based on general statutory rules for the jurisdictions listed. Actual deadlines may vary due to weekends, public holidays, individual extensions, agent lodgement schedules, or legislative changes. All dates must be verified by a credentialed professional in the relevant jurisdiction before reliance. OpenAccountants does not guarantee the accuracy of any deadline and accepts no liability for late filings. This is not legal or tax advice.

Section 1 -- Scope statement

This skill covers:

• Jurisdictions: US (federal + CA), MT, GB, DE, AU, CA (Canada), IN, ES, NL, SG (15 jurisdiction-obligation combinations)
• Obligation types: Income tax, estimated/provisional tax, VAT/GST/BTW, social security contributions
• Output: Sorted 12-month calendar, urgency flags, penalty estimates

This skill does NOT cover:

• Corporate tax returns, payroll obligations, or employer filings
• Extension requests or amended return deadlines (beyond noting extension availability)
• Sub-national deadlines beyond US-CA (other US states, German Laender, Australian states, etc.)
• Deadlines for obligations not listed in the master table

Section 2 -- Workflow

Step 0 -- Read the user's obligation profile

0. Read obligation profile — Read the user's jurisdiction and obligation types from one of these sources, in priority order: 1. Intake manifest -- the structured output from an intake skill (e.g., us-ca-freelance-intake) 2. Explicit user statement -- "I'm a freelancer in Malta" or "I file in the UK and Germany" 3. Prior conversation context -- jurisdiction identified in an earlier turn If no jurisdiction can be determined, ask: > "Which country (or countries) do you file taxes in? And what types of obligations do you have -- income tax, VAT/GST, estimated tax payments, social security?" Do not proceed until at least one jurisdiction is confirmed.

Step 1 -- Look up filing deadlines

0. Look up deadlines — Match the user's jurisdiction + obligation types against the Master Deadline Table in Section 3. Pull every matching row.

Step 2 -- Generate the calendar

0. Generate calendar — 1. Anchor to today's date. 2. For each matched obligation, compute the next 12 months of concrete deadline dates. 3. Adjust for weekends: if a deadline falls on a Saturday, move to the preceding Friday; if on a Sunday, move to the following Monday -- unless the jurisdiction has a different convention (noted in the table). 4. Sort all deadlines chronologically. 5. Present as a table: | # | Date | Jurisdiction | Obligation | Form | Action required | Urgency | |---|------|--------------|------------|------|-----------------|---------|

Step 3 -- Flag approaching deadlines

0. Flag deadlines — Apply urgency flags based on days until deadline from today's date. If any deadline is OVERDUE, add a penalty estimate (Step 4) automatically.

Urgency flag table (Section 3 -- Master Deadline Table (urgency flag table))

Days remaining	Flag	Label
> 30 days	--	On track
8--30 days	AMBER	Approaching
0--7 days	RED	Urgent
Past due	RED	OVERDUE

Step 4 -- Calculate penalties for late filing

0. Calculate penalties — When a deadline is past due or when the user asks "what if I file late?", compute the estimated penalty using the jurisdiction's penalty rules. Reference the relevant content skill for precise penalty logic. If no content skill is loaded for that jurisdiction, use the penalty summary in Section 4 of this file and flag the estimate as T2 (reviewer judgment required). Always state: "Penalty estimates are approximations. Actual penalties depend on the amount of tax owed, the length of delay, and jurisdiction-specific rules. A credentialed professional should confirm."

Section 3 -- Master Deadline Table

3.1 United States -- Federal

US Federal deadline table (3.1 United States -- Federal)

Obligation	Form	Frequency	Deadline	Notes
Federal income tax (filing + payment)	1040	Annual	Apr 15	Auto-extends to Oct 15 for filing (not payment) via Form 4868
Estimated tax -- Q1	1040-ES	Quarterly	Apr 15	Based on prior-year or current-year liability
Estimated tax -- Q2	1040-ES	Quarterly	Jun 15
Estimated tax -- Q3	1040-ES	Quarterly	Sep 15
Estimated tax -- Q4	1040-ES	Quarterly	Jan 15 (next year)

3.2 United States -- California

US California deadline table (3.2 United States -- California)

Obligation	Form	Frequency	Deadline	Notes
CA individual income tax	540	Annual	Apr 15	Conforms to federal date; auto-extends to Oct 15
CA SMLLC annual tax	568	Annual	Apr 15	$800 minimum franchise tax due regardless of income
CA estimated tax	540-ES	Quarterly	Apr 15, Jun 15, Sep 15, Jan 15	30/40/0/30 schedule

3.3 Malta

Malta deadline table (3.3 Malta)

Obligation	Form	Frequency	Deadline	Notes
Income tax return	TA24	Annual	Jun 30	For self-employed / self-occupied
VAT return	Periodic return (CFR)	Quarterly	45 days after quarter end	Quarters: Jan-Mar, Apr-Jun, Jul-Sep, Oct-Dec
Social security contributions (Class 2)	SSC	Quarterly	Apr 30, Jul 31, Oct 31, Jan 31	Self-occupied persons
Provisional tax -- 1st instalment	PT	Annual	Apr 30	20% of prior-year liability
Provisional tax -- 2nd instalment	PT	Annual	Aug 31	30% of prior-year liability
Provisional tax -- 3rd instalment	PT	Annual	Dec 21	50% of prior-year liability

3.4 United Kingdom

United Kingdom deadline table (3.4 United Kingdom)

Obligation	Form	Frequency	Deadline	Notes
Self Assessment (online)	SA100	Annual	Jan 31	For tax year ending prior Apr 5
Self Assessment (paper)	SA100	Annual	Oct 31	Paper filing deadline
Payment on Account -- 1st	POA	Semi-annual	Jan 31	50% of prior-year liability
Payment on Account -- 2nd	POA	Semi-annual	Jul 31	50% of prior-year liability
Balancing payment	SA100	Annual	Jan 31	Difference from POAs
VAT return	VAT100	Quarterly	1 month + 7 days after quarter end	Making Tax Digital; quarters vary by stagger group

3.5 Germany

Germany deadline table (3.5 Germany)

Obligation	Form	Frequency	Deadline	Notes
Income tax return	ESt (Einkommensteuererklaerung)	Annual	Jul 31	Extends to end of Feb (+2 years) if filed by Steuerberater
VAT return (advance)	UStVA (Umsatzsteuer-Voranmeldung)	Monthly or Quarterly	10th of following month	Monthly if prior-year VAT > EUR 7,500; quarterly if EUR 1,000--7,500
VAT annual return	UStE	Annual	Jul 31	Reconciliation return
Estimated tax -- Q1	Vorauszahlung	Quarterly	Mar 10	Based on Vorauszahlungsbescheid
Estimated tax -- Q2	Vorauszahlung	Quarterly	Jun 10
Estimated tax -- Q3	Vorauszahlung	Quarterly	Sep 10
Estimated tax -- Q4	Vorauszahlung	Quarterly	Dec 10

3.6 Australia

Australia deadline table (3.6 Australia)

Obligation	Form	Frequency	Deadline	Notes
Income tax return (self-lodged)	ITR	Annual	Oct 31	For FY ending Jun 30
Income tax return (tax agent)	ITR	Annual	May 15	Agent lodgement programme; dates vary
BAS -- GST (quarterly)	BAS	Quarterly	28th of month after quarter end	Quarters: Jul-Sep, Oct-Dec, Jan-Mar, Apr-Jun
PAYG instalments	BAS/IAS	Quarterly	28th of month after quarter end	Lodged with BAS if registered for GST

3.7 Canada

Canada deadline table (3.7 Canada)

Obligation	Form	Frequency	Deadline	Notes
Individual income tax (filing)	T1	Annual	Jun 15	Extended filing date for self-employed
Individual income tax (payment)	T1	Annual	Apr 30	Balance owing due regardless of filing deadline
GST/HST return	GST34	Quarterly or Annual	End of month after reporting period	Annual filers: Jun 15 (sole prop)
Instalments -- Q1	--	Quarterly	Mar 15	Required if net tax owing > CAD 3,000
Instalments -- Q2	--	Quarterly	Jun 15
Instalments -- Q3	--	Quarterly	Sep 15
Instalments -- Q4	--	Quarterly	Dec 15

3.8 India

India deadline table (3.8 India)

Obligation	Form	Frequency	Deadline	Notes
Income tax return (no audit)	ITR-3 or ITR-4	Annual	Jul 31	ITR-4 for presumptive taxation
Income tax return (audit required)	ITR-3	Annual	Oct 31	If turnover exceeds audit threshold
Advance tax -- Q1	Challan 280	Quarterly	Jun 15	15% of estimated liability
Advance tax -- Q2	Challan 280	Quarterly	Sep 15	45% cumulative
Advance tax -- Q3	Challan 280	Quarterly	Dec 15	75% cumulative
Advance tax -- Q4	Challan 280	Quarterly	Mar 15	100% cumulative
GST return	GSTR-3B	Monthly	20th of following month	Summary return with tax payment
GST annual return	GSTR-9	Annual	Dec 31	If turnover > INR 2 crore

3.9 Spain

Spain deadline table (3.9 Spain)

Obligation	Form	Frequency	Deadline	Notes
IRPF (income tax)	Modelo 100	Annual	Jun 30	Renta campaign typically opens Apr 2
IVA (VAT) -- Q1	Modelo 303	Quarterly	Apr 20
IVA (VAT) -- Q2	Modelo 303	Quarterly	Jul 20
IVA (VAT) -- Q3	Modelo 303	Quarterly	Oct 20
IVA (VAT) -- Q4	Modelo 303	Quarterly	Jan 30	Note: Jan 30, not Jan 20
Pago fraccionado -- Q1	Modelo 130	Quarterly	Apr 20	20% of cumulative net income
Pago fraccionado -- Q2	Modelo 130	Quarterly	Jul 20
Pago fraccionado -- Q3	Modelo 130	Quarterly	Oct 20
Pago fraccionado -- Q4	Modelo 130	Quarterly	Jan 30
RETA (social security)	Cuota	Monthly	Last business day of month	Autonomous workers' regime

3.10 Netherlands

Netherlands deadline table (3.10 Netherlands)

Obligation	Form	Frequency	Deadline	Notes
Income tax return	IB (Inkomstenbelasting)	Annual	May 1	Can request extension to Sep 1
BTW (VAT) return	Aangifte omzetbelasting	Quarterly	Last day of month after quarter end	Quarters: Jan-Mar, Apr-Jun, Jul-Sep, Oct-Dec
Voorlopige aanslag (provisional assessment)	--	As assessed	Per Belastingdienst schedule	Monthly instalments based on assessment

3.11 Singapore

Singapore deadline table (3.11 Singapore)

Obligation	Form	Frequency	Deadline	Notes
Income tax return	Form B	Annual	Apr 18 (e-filing) / Apr 15 (paper)	For year of assessment (prior calendar year)
GST return	GST F5	Quarterly	1 month after quarter end	Prescribed accounting periods
Estimated chargeable income	ECI	Annual	3 months after FY end	For companies only; individuals use Form B

Section 4 -- Penalty summaries (for late-filing estimates)

These are simplified penalty rules for estimation purposes. Always flag as T2 and recommend reviewer verification.

US -- Federal

• Failure to file (FTF) — 5% of unpaid tax per month, max 25%. Minimum penalty for returns >60 days late: lesser of $510 or 100% of unpaid tax. (US -- Federal)
• Failure to pay (FTP) — 0.5% of unpaid tax per month, max 25%. (US -- Federal)
• Estimated tax underpayment — IRC section 6654 penalty calculated at federal short-term rate + 3 percentage points, compounded daily. (US -- Federal, IRC section 6654)

US -- California

• Late filing — 5% of tax due + 0.5% per month (max 25%). Minimum $135 or 100% of tax. (US -- California)
• Late payment — Collection cost recovery fee applies after demand notice. (US -- California)

Malta

• Late filing of TA24 — Administrative penalty of EUR 50 per month or part thereof (max EUR 500). (Malta)
• Late payment — Interest at 0.54% per month on unpaid tax. (Malta)
• Late VAT return — EUR 20 per day of delay. (Malta)

United Kingdom

• Late SA filing — GBP 100 immediate; after 3 months, GBP 10/day (max 90 days = GBP 900); after 6 months, 5% of tax due or GBP 300 (whichever is greater); after 12 months, further 5% or GBP 300. (United Kingdom)
• Late payment — 5% surcharge at 30 days, 6 months, and 12 months past due. (United Kingdom)

Germany

• Late filing (Verspaetungszuschlag) — 0.25% of assessed tax per month of delay, minimum EUR 25/month. (Germany)
• Late payment (Saumniszuschlag) — 1% per month of the rounded-down tax amount. (Germany)

Australia

• Failure to lodge on time: one penalty unit per 28-day period or part period, capped at 5 units before the applicable multiplier. At AUD 364 per unit for infringements on or after 1 July 2026, the base cap is AUD 1,820. Individuals and small withholders can still meet the income or current GST turnover tests for a higher multiplier. Verify the penalty unit for the infringement date and apply the alternative tests and special rules in au-lodgment-deadlines-penalties. TAA 1953 (Cth) sch 1 s 286-80. (Australia)
• General interest charge (GIC) — Base rate + 7 percentage points, compounded daily. (Australia)

Canada

• Late filing — 5% of balance owing + 1% per complete month late (max 12 months = 17% total). (Canada)
• Repeated late filing — 10% + 2% per month (max 20 months). (Canada)
• Instalment interest — Prescribed rate, compounded daily. (Canada)

India

• Late filing (section 234F) — INR 5,000 if filed by Dec 31; INR 10,000 after. INR 1,000 if total income < INR 5 lakh. (India, section 234F)
• Late payment interest (section 234B) — 1% per month on shortfall. (India, section 234B)
• Advance tax interest (section 234C) — 1% per month on quarterly shortfall. (India, section 234C)

Spain

• Late filing (recargo) — 1% + 1% per complete month of delay (up to 12 months), no penalties/interest. After 12 months: 15% surcharge + interest. (Spain)
• Late payment — 5% (3 months), 10% (6 months), 15% (12 months), 20% + interest (>12 months). Under the new LGT reform, voluntary regularisation recargos apply. (Spain)

Netherlands

• Late filing — EUR 385 fixed penalty (verzuimboete). Repeated: up to EUR 5,514. (Netherlands)
• Late payment — Tax interest (belastingrente) at 7.5% (2025 rate for income tax). (Netherlands)

Singapore

• Late filing — SGD 200 immediate; if still not filed after 1 month, summons + further penalties up to SGD 1,000. (Singapore)
• Late payment — 5% penalty on unpaid tax. After 1 month: additional 1% per month (max 12%). (Singapore)

Section 5 -- Output format

Present the calendar in this structure:

Part A -- Filing calendar (next 12 months)

Filing calendar table (Part A) (Part A -- Filing calendar (next 12 months))

#	Date	Days	Urgency	Jurisdiction	Obligation	Form	Action
1	2026-04-15	4	RED	US	Federal income tax	1040	File return + pay balance
2	2026-04-15	4	RED	US	Estimated tax Q1	1040-ES	Pay Q1 estimate
...

Part B -- Overdue items (if any)

List any obligations past their deadline with estimated penalty.

Part C -- Reviewer notes

• Assumptions made (e.g., "assumed online filing for UK SA100")
• Items requiring reviewer confirmation
• Suggestions for extension filings

Section 6 -- Self-checks

Before delivering output, verify:

• User's jurisdiction is confirmed, not assumed
• All obligations for the jurisdiction are included (none omitted)
• Dates are correct for the current calendar year
• Weekend adjustment applied where needed
• Urgency flags match the days-remaining calculation
• Penalty estimates are flagged T2 with reviewer disclaimer
• No filing advice is given without reviewer qualification
• Calendar is sorted chronologically
• Output uses the format from Section 5

Disclaimer

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.