Self Assessment Tax Return & Payments on Account Check

If you work for yourself, Self Assessment is how you tell HMRC what you earned and pay the Income Tax and Class 4 National Insurance on your profits. Under the Taxes Management Act 1970 you must tell HMRC you need to file by 5 October after the tax year ends (s.7), send your return by 31 October on paper or 31 January online (s.8), and pay any balance by 31 January (s.59B). Once your bill passes £1,000, HMRC usually also asks for two advance payments on account towards next year, each half of this year’s bill, due on 31 January and 31 July (s.59A). Many first-year freelancers are caught out because their first January bill covers a full year’s tax plus the first payment on account for the next year.

Missing dates is expensive. Under Schedule 55 to the Finance Act 2009 a late return gets an automatic £100 penalty, then £10 a day after three months (up to £900), then further penalties at six and twelve months. Under Schedule 56, unpaid tax attracts 5% surcharges at 30 days, six months and twelve months, and HMRC charges late payment interest at the Bank of England base rate plus 4% (since April 2025). You also need to keep records for at least five years after the 31 January filing deadline (s.12B). This check shows where you stand and what to sort out before the next deadline.

Use this free tool to check your Self Assessment position as a sole trader or freelancer: whether you need to file, which deadlines apply, whether payments on account will hit you in January, and what to do now to avoid penalties.