Answers · UK 2025/26

How much is the penalty for filing a Self Assessment tax return late?

Filing your Self Assessment return even one day after the 31 January deadline triggers an automatic £100 penalty, even if you owe no tax or are due a refund. Further penalties of £10 a day apply after 3 months (capped at £900), with additional 5% or £300 penalties (whichever is greater) at 6 and 12 months if the return is still outstanding.

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HMRC applies escalating penalties for late Self Assessment tax returns, which are separate from and in addition to any penalties or interest charged for paying the tax itself late. **The escalating penalty schedule** 1. **1 day late**: automatic £100 fixed penalty, applied even if you have no tax to pay or are owed a refund -- the penalty is for the late return itself, not late payment. 2. **3 months late**: daily penalties of £10 a day, up to a maximum of 90 days (£900), on top of the initial £100 -- so by day 93 you could owe £1,000 in filing penalties alone. 3. **6 months late**: a further penalty of the greater of £300 or 5% of the tax due. 4. **12 months late**: another further penalty of the greater of £300 or 5% of the tax due (in serious cases of deliberate withholding, this can rise to 100% of the tax due instead). **Worked example: return filed 4 months late, £2,000 tax owed** - £100 fixed penalty (day 1) - £10/day × 30 days (the extra month past the 3-month mark) = £300 - Total so far: £400, before any 6-month or 12-month penalties would apply if it remained unfiled **Worked example: return filed on 1 February (1 day late), no tax owed** Even though no tax is due, the taxpayer still receives the automatic £100 penalty simply for missing the 31 January deadline -- having no tax liability does not exempt you from the filing penalty. **Separate late PAYMENT penalties and interest** On top of filing penalties, if you also pay your tax bill late, HMRC charges late payment penalties (typically starting at 30 days late) plus daily interest on the outstanding amount from the original due date, calculated separately from the filing penalties above. **Reasonable excuse** You can appeal a penalty if you have a "reasonable excuse" -- HMRC gives examples such as a partner or close relative dying shortly before the deadline, an unexpected stay in hospital, a serious IT failure just before filing, or a fire/flood/theft preventing you from completing your return. Simply forgetting, finding the return too complicated, or your accountant being late are generally NOT accepted as reasonable excuses. **How to avoid penalties** File as early as possible after the tax year ends (6 April), even if you cannot pay the tax immediately -- filing on time avoids the return penalties even if you then need to set up a Time to Pay arrangement for the tax itself.