Extended Federal 1040 Deadline

Final deadline to file Form 1040 if you requested an extension via Form 4868 in April. Tax owed was still due April 15.

Filing deadline

October 15, 2026

Country: United States
Tax year: 2025
Official: Tax authority

What is this deadline?

The hard deadline to file Form 1040 for tax year 2025 if you filed Form 4868 by April 15 to get a 6-month extension.

Who needs to file?

Anyone who extended their return. An extension is of time to file, not time to pay — any balance due was already owed on April 15 and has been accruing failure-to-pay penalties and interest since.

What people miss

This is the last chance to fund a Solo 401(k) employer contribution or SEP-IRA for 2025 tax year
Make sure Solo 401(k) plan was established before Dec 31, 2025 even if funded later
If you can't file by October 15, there's no further extension except for specific disaster relief or combat zone rules

Prepare this return with open-source skills

These skills are in the OpenAccountants repo. Clone them into Claude, Cursor, or any AI agent and they handle the computation.

us-federal-return-assembly.mdUS

Tier 2 orchestrator skill that assembles the complete federal income tax return package for US freelance software developers filing as sole proprietors or single-member LLCs disregarded for federal tax. Sequences the upstream content skills (bookkeeping, SE computation, retirement, SE health insurance, QBI, estimated tax) in dependency order, resolves circular computations between SE health insurance and retirement contributions, produces Form 1040 with all required schedules (Schedule 1, Schedule 2, Schedule 3, Schedule C, Schedule SE, Schedule D if needed, Form 8829, Form 4562, Form 8995 or 8995-A, Form 8962 if marketplace coverage, Form 2210 if penalty, Form 7206), performs cross-form reconciliation checks, and produces the final reviewer package. Does not itself compute tax amounts — delegates to upstream content skills. MUST be loaded alongside us-tax-workflow-base v0.2 or later and all content skills it orchestrates. Federal only.

This page is informational only and not tax advice. Verify dates and requirements against the official tax authority before filing.

Q3 Estimated Tax (Form 1040-ES)

All United States deadlines Global calendar