Self Assessment deadlines and penalties: the dates that matter

Every year, hundreds of thousands of people miss the Self Assessment deadline and pay HMRC penalties they could easily have avoided. Here are the dates that matter, and what each one costs if you miss it.

The key dates

• 5 October — register for Self Assessment if you are newly self-employed or have new untaxed income
• 31 October — paper tax return deadline
• 31 January — online tax return deadline, balancing payment for the previous year, and first payment on account
• 31 July — second payment on account
• 5 April — the end of the tax year

What late filing costs

A return that is 12 months late can attract penalties of £1,600 or more — before interest on any unpaid tax. Late payment interest is charged from the due date as well.

• 1 day late — an immediate £100 penalty, even if you owe no tax
• 3 months late — £10 per day, up to £900
• 6 months late — a further 5% of the tax due or £300, whichever is greater
• 12 months late — another 5% or £300, whichever is greater

Payments on account catch people out

If your Self Assessment bill is over £1,000, HMRC usually asks for advance payments towards next year’s bill: half on 31 January and half on 31 July. First-year filers are often surprised by a January bill that is roughly 150% of what they expected. Planning for this in advance removes the shock.

The simple way to never pay a penalty

File early. We complete most clients’ returns within weeks of the tax year ending in April — nine months before the deadline. You know exactly what you owe, you can budget for it, and the January panic simply never happens. If you are already behind, we specialise in catching up overdue returns and dealing with HMRC on your behalf.