Self Assessment Deadlines
Key dates for filing and payment. Missing these can mean automatic penalties, so plan ahead.
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31 January deadline explained
The most important date in the Self Assessment calendar. What you need to submit, when to pay, and what happens if you miss it.
Payments on account explained
Two advance payments towards a future Self Assessment bill, usually due 31 January and 31 July. When they apply and how to reduce them.
Late filing penalties
How late filing penalties build up: the £100 immediate fine, daily penalties, and 6 and 12 month escalations.
The dates, in the order they arrive
5 October: register if this is your first year. 31 October: paper filing deadline. 30 December: file by now if you want a smaller bill collected through your PAYE code. 31 January: online filing, the balancing payment, and the first payment on account. 31 July: the second payment on account.
Every one of these keys off the tax year that ended the previous 5 April. The return filed by 31 January 2027 reports the year ended 5 April 2026.
Why January is really three deadlines
31 January stacks the return, last year's balancing payment, and the first advance payment for the current year into one date. For a first-time filer with a bill over £1,000, that means eighteen months of tax falling due at once — the famous first-year shock.
It is entirely predictable, which means it is entirely plannable. Knowing the number by autumn turns January from a cliff into a diary entry.
Filing early changes nothing except the stress
The payment date does not move when you file early. File in May and you still pay in January — but you know the exact bill eight months ahead, your tax code options stay open, and any refund comes back immediately rather than in the January queue.
There is no advantage whatsoever to filing in January. That the majority of returns arrive then is a habit, not a strategy.
Deadline Lock, applied to Self Assessment
Every RR client's registration, filing, and payment dates are tracked in Deadline Lock with advance notification — and returns are prepared from year-round records, so the deadline we manage is HMRC's, not the calendar's last page.
Frequently asked questions
What if 31 January falls on a weekend?
The deadline does not move. Online filing is open around the clock, and payment must reach HMRC by the day itself — so treat the last banking day before as the real payment deadline if you are using a standard transfer.
Is the paper deadline really three months earlier?
Yes — 31 October against 31 January online. The earlier date is one of several reasons paper filing has almost disappeared; unless you have a specific reason, file online and keep the extra three months.
What does filing by 30 December get me?
If your balance is under £3,000 and you have PAYE income, HMRC can collect it through next year's tax code instead of as a lump sum — interest-free, spread across twelve months. File after 30 December and that option is gone for the year.
When do payments on account fall due?
31 January and 31 July, each 50% of last year's bill, whenever that bill exceeded £1,000 and less than 80% was collected at source. They are advances against the current year, trued up in the following January's balancing payment.