Self Assessment: avoid the October scramble

TL;DR: Deadlines creep up while paperwork multiplies. Self-assessment season is here again, but it doesn’t have to end in panic. Here’s how to get ahead of the October rush.

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Worried businesswoman working from home on a laptop as deadlines approach

Deadlines creep up while paperwork multiplies. If you’ve had a change in circumstances—new dividends, a rental property, a sale of shares, or a side-gig—your Self Assessment can shift from routine to risky. Paper returns must reach HMRC by 31 October; online filing runs to 31 January. Miss either and you risk penalties and interest that are avoidable with a little structure. The fastest route is simple: gather the right documents, check your allowances, and avoid the traps that pull otherwise organised people into HMRC’s enquiry net. Below, you’ll find a short checklist you can follow today. It’s deliberately practical, with plain-English prompts you can tick off in under an hour.

What changed / who’s affected

  • Anyone with new or irregular income (dividends, rent, capital gains, self-employment).

  • Higher-rate taxpayers who might reclaim/add adjust child benefit or gift aid.

Your fast prep checklist

  1. Documents: P60/P45, P11D, interest/dividend statements, rental ledgers, CIS statements, pension contributions, CGT records.

  2. Allowances: personal savings/dividend allowances; property allowances; trading allowance for small side-income.

  3. Deductions: pension contributions, gift aid, professional fees where allowable, mileage vs actual costs.

  4. Capital gains: check annual exemption and bed-and-ISA actions; keep contract notes.

  5. Payments on account: recalc to avoid over/under-paying for the current year.

  6. Before you submit: sanity-check NI number, UTR, bank details; compare to last year’s figures for anomalies.

Common pitfalls

  • Missing student loan boxes (creates unexpected bills).

  • Forgetting overseas income from platforms/brokers.

  • Claiming expenses without records. Keep digital copies.

Further reading (add links): GOV.UK — Self Assessment deadlines; HMRC guidance; penalties overview.

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