What happens if I miss a Self-Assessment tax return deadline?

Filing a late tax return is a bad move, and it’s all too common. You’ve got until the 31st of January to file your tax return online, then until the 31st of July to make your payment on account, and you can expect HMRC to chase you if you miss either deadline. The penalties for failing to file your return or pay the tax you owe can be severe and painful, so it’s essential that you keep up.

Missing a filing deadline by just one day means you're already facing an automatic fine of £100.

After that, things just keep getting worse. Depending on which deadline you've missed, you could be looking at daily penalties or fines based on a percentage of the tax you owe. Worse still is the possibility that HMRC decides you're trying to cheat your way out of paying up. Getting caught in the sights of an HMRC investigation isn’t fun, and can lead to some serious consequences.