Tax Year Dates and Deadlines for 2026-2027

The UK tax year runs from 6 April to 5 April, and if you're filing a Self Assessment return, your deadline is 31 January (online) or 31 October (paper). In the US, the tax year follows the calendar year (1 January to 31 December), and your federal income tax return is due 15 April — known as Tax Day. Miss these dates and HMRC or the IRS will charge penalties. So here's exactly what to file, when to file it, and what happens if you're late.

UK Tax Year Dates and Key Deadlines

The UK tax year doesn't follow the calendar. It runs from 6 April in one year to 5 April the next year. For the 2026/27 tax year, that's 6 April 2026 to 5 April 2027. This quirk matters because:

Your annual income is calculated on this cycle—not January to December
All your allowances and tax bands reset on 6 April
Tax returns are filed after the tax year ends, based on the full year's income

Self Assessment deadlines (2026/27 tax year):

31 October 2026: Paper tax returns must arrive at HMRC
31 January 2027: Online returns and payment deadline. If you owe tax, pay by this date to avoid interest
31 July 2027: Second payment on account (for self-employed people whose tax bill exceeds £1,000)

Other key dates:

6 April 2026: The 2025/26 tax year ends; 2026/27 begins
5 April 2027: Last day of the 2026/27 tax year

Miss 31 January and HMRC charges a £100 penalty immediately, then £10 per day if you're still late 6 months later. If you owe tax and don't pay by 31 January, interest accrues at 8.75% annually.

US Tax Year and Filing Deadline

In the US, the tax year is straightforward: 1 January to 31 December. Your federal income tax return is due 15 April of the following year.

Key US deadlines (for tax year 2026):

15 April 2027: Federal income tax return (Form 1040) is due
15 April 2027: Estimated quarterly tax payments are due if you're self-employed or have other income not subject to withholding
15 October 2027: Extended deadline if you file for an extension (Form 4868)
State deadlines vary: Most states follow the federal 15 April date or extend to mid-June

Unlike the UK, US deadlines are tied to fixed calendar dates. When 15 April falls on a weekend, it shifts to the next business day.

If you're self-employed, you also need to make quarterly estimated tax payments on:

15 April (Q1)
15 June (Q2)
15 September (Q3)
15 January of the next year (Q4)

Shortfall in withholding? You'll owe penalties and interest on the underpayment.

Understanding Your Tax Bands and How They Reset

Why do tax year dates matter so much? Because on 6 April (in the UK), HMRC resets your tax allowances and thresholds. Here's what applies in 2026/27:

UK tax bands (2026/27):

Personal allowance: £0–£12,570 at 0%
Basic rate: £12,571–£50,270 at 20%
Higher rate: £50,271–£125,140 at 40%
Additional rate: £125,141+ at 45%

These are marginal rates—only the income within each band is taxed at that rate. Earn £60,000? You pay 0% on the first £12,570, then 20% on everything up to £50,270, then 40% on the remainder. Your effective rate is roughly 19%, not 40%.

If you're tracking your tax liability throughout the year or planning tax relief, you need to know which year's allowances apply to you. The tax-free personal allowance and other allowances reset on 6 April, so your available relief changes at that date. Read more about UK tax-free allowances to understand what you're entitled to claim.

For the US vs UK tax system, the structure is different—the US uses a different calendar, different thresholds, and different terminology—but the principle is identical: you only pay tax on income above certain points.

Practical Checklist for Your Tax Year

For employees: Check your payslip each month. Your tax code (usually 1257L) tells HMRC to give you a £12,570 personal allowance. If your code is different—say 1000L or 057L—you're being under-alloc'd and paying too much tax. Contact HMRC to correct it; they can backpay you.

For self-employed (sole trader or partnership):

Set aside 25–30% of profit every month for tax. January is too late to scramble for money.
Keep invoices, receipts, mileage logs, and bank statements for all 6 years. HMRC can audit back 4 years by default (6 years if they suspect carelessness).
File by 31 January for a smooth return. Late? You're into penalty territory.
Plan for two payments: one on 31 January (previous year's tax) and one on 31 July (payment on account for the current year).

For limited companies:

Corporation tax is due 9 months after your accounting year-end.
File your accounts with Companies House within 9 months of year-end.
File your corporation tax return with HMRC within 12 months of year-end.

Learn more about calculating corporation tax in the UK.

For everyone:

Claim tax relief on professional subscriptions—accountancy fees, professional memberships, training courses are all deductible.
Claim tax relief on charitable donations. Donate to a UK registered charity? You can claim 20% back (higher rate taxpayers claim 20% via self-assessment).
Keep records digitally. HMRC requires electronic records if your turnover exceeds £10,000. Even phone photos of hand-written notes count.

Common Tax Deadline Mistakes

Submitting late and ignoring the penalty. HMRC charges £100 for filing 3+ months late, even if you don't owe tax. File on time.

Not keeping records in the right format. HMRC requires digital records for all but the smallest businesses. Photos of receipts on your phone are fine; but "I lost the invoices" is not.

Forgetting to claim mileage. Drive for work? Claim 45p per mile for the first 10,000 miles, then 25p after. That's often worth £200–£500 yearly.

Missing the dividend allowance. Own a company or receive dividends? The first £500 of dividend income is tax-free. Most people don't claim this—you should.

Not asking for an extension. If you know you'll miss 31 January, contact HMRC. They'll often grant an extension to 28 February or beyond if you have a reasonable excuse. No penalty. Missing the deadline without asking? Penalty applies.

Overlooking the July payment deadline. If you're self-employed and your tax bill exceeds £1,000, you'll owe two payments: January and July. The July payment is easy to forget. Set a calendar reminder.

Frequently Asked Questions

Q: What happens if I file my Self Assessment after 31 January? A: You'll be charged a £100 penalty immediately for filing late. If you're still late after 6 months, HMRC charges £10 per day. If you owe tax, interest accrues at 8.75% from 31 January until payment.

Q: Do I have to file a tax return? A: Only if HMRC sends you a notice, or if you're self-employed, or if you have income from multiple sources, or if you're a company director. Employees on PAYE with only a salary don't usually file unless they have additional income.

Q: What's the difference between the UK tax year (6 April – 5 April) and the calendar year? A: The UK tax year is a historical legacy. The US uses the calendar year (1 January – 31 December). This matters when comparing international income or filing cross-border tax returns. Deadlines, thresholds, and filing requirements differ significantly.

Q: Can I get an extension on the 31 January deadline? A: Contact HMRC before the deadline. They'll often grant an extension to 28 February or beyond if you have a good reason (illness, overseas travel, system failure). If they approve it, you won't face a penalty. Submitting late without asking? Penalties apply.

Q: What's a "payment on account" and when do I pay it? A: If your Self Assessment tax bill was over £1,000 in the previous year, HMRC assumes you'll owe a similar amount this year and asks for payment in two instalments: one on 31 January and one on 31 July. If you earn less, you can reduce these payments by updating your tax account online or calling HMRC.

Q: What if I file my US return after 15 April? A: You'll owe a failure-to-file penalty of 5% of unpaid tax per month (up to 25%), plus interest. The IRS will take enforcement action if you owe a significant amount. Filing for an extension (Form 4868) gives you until 15 October, but note: an extension to file is not an extension to pay. Your payment deadline is still 15 April.

Q: Are there any tax deadlines mid-year (other than quarterly payments)? A: In the UK, the main mid-year date is 19 April, when HMRC typically adjusts tax codes if they've found errors. Check your payslip in April to see if your code changed. No action needed—it's automatic. In the US, quarterly estimated tax payments (for self-employed people) are due 15 April, 15 June, 15 September, and 15 January.

Q: What happens if I miss the July payment deadline in the UK? A: You'll be charged interest on the late payment at 8.75% per annum. If you continue to miss payments, HMRC can pursue enforcement—they can issue a County Court Judgment, take money straight from your bank, or pursue a Magistrate's Order. If you can't pay, contact HMRC to discuss a payment plan.

Next Steps

Mark these key dates in your calendar now—particularly 31 January (Self Assessment deadline) and 6 April (start of the new tax year). Use our sales tax calculator to estimate your tax bill and see what you'll owe based on your income and deductions.

For more information, check HMRC's Self Assessment deadlines page (UK) or the IRS when-to-file guidance (US). Citizens Advice offers free tax guidance at citizensadvice.org.uk, and HMRC's helpline is available at 0300-200-3310.