Self Assessment 2025/26 deadlines & a stress-free checklist
All the dates that matter, what HMRC actually needs, and how to avoid the £100 late filing penalty.
Key dates
5 October 2026 — register for Self Assessment if it's your first year. 31 October 2026 — paper returns due. 31 January 2027 — online returns and any tax owed. 31 July 2027 — second payment on account, if applicable.
What you'll need
P60s and P45s, dividend vouchers, rental income statements, business income & expenses, pension contributions, gift aid donations, student loan plan type, and your UTR number.
Avoiding the penalty
Even if you can't pay the bill, file the return on time — that alone avoids the £100 fixed penalty. HMRC's Time to Pay arrangement is widely available for tax debts under £30k.
Ready to talk to a real accountant?
Create a private structured brief for eligible UK firms. Free for clients, with no obligation to appoint.
Get free quotes