HMRC Self-Assessment Deadlines Cheat Sheet

Self-Assessment has more deadlines than most people realise, and missing one costs you. Give it the tax year and you get the full calendar: registration, paper and online return dates, the balancing payment, both payments on account, the amendment window and the claim deadlines. One list, so nothing creeps up on you.

Produce a complete, authoritative calendar of every UK Self-Assessment deadline I need to know for the {TAX_YEAR} tax year. Include: the deadline to register for Self-Assessment if self-employed, the paper return deadline, the online return deadline, the payment deadline for balancing payments, the payment on account deadlines (31 January and 31 July), the deadline for amending a submitted return, and the deadline to claim overpaid tax refunds. For each deadline, state what happens if I miss it, including the automatic penalty structure (late filing and late payment) and how interest accrues. Format as a chronological table with deadline, description, and consequence columns.