When is the self assessment deadline?

The 31 January deadline is also usually the deadline for paying any balancing tax due for the previous tax year, plus the first payment on account if one applies.

Leaving records until the final weeks increases the risk of missing income, claiming expenses incorrectly, or discovering a tax bill too late to plan cash flow.

The return covers income and gains from 6 April 2025 to 5 April 2026. If you are new to Self Assessment, you would normally tell HMRC by 5 October 2026. The standard paper deadline is 31 October 2026 and the online filing and payment deadline is 31 January 2027.

If you want HMRC to consider collecting a qualifying bill through a PAYE tax code, the online return generally needs to be submitted by 30 December 2026. Eligibility and limits apply, so filing by that date does not guarantee that coding is available.

A January payment can contain two different amounts: the balancing payment for the year just filed and the first payment on account towards the following year. A second payment on account is normally due on 31 July. HMRC explains when payments on account apply and how each instalment is calculated.

If current-year income has genuinely fallen, it may be possible to ask HMRC to reduce payments on account. Reducing them too far can result in interest on the shortfall, so base the request on a defensible forecast rather than cash-flow pressure alone.

Not every return follows the headline dates. HMRC may issue a notice to file late in the cycle with a deadline stated in the notice, and some partnership or trustee returns have different filing routes. Always follow the date shown in your HMRC account or correspondence if it differs.

A late return can trigger a filing penalty even when no tax is due. Late payment can create separate interest and penalties. File and pay as soon as possible, and use HMRC’s appeal process if you believe you have a reasonable excuse.