Deadline to file your tax return online: This is the final deadline for you to fill in and send your online tax returns to HMRC. If you didn’t register online before the 5th October you’ll need to submit your return at least 20 working days beforehand as you’ll need to register first.
Deadline for first ‘payments on account’: Payments on account are advance payments you need to pay towards your tax bill. Usually you’ll need to make two payments on account every year – one on 31st January and the other on 31st July. Each payment is half your previous year’s tax bill – in other words they’re a prediction of what your tax bill will be, based on the year before.
Deadline for ‘balancing payments’: Paying tax you owe for the previous year. If you still need to pay tax after you’ve made your payments on account the year before – because your tax bill for the last year actually turned out higher than it was the year before that – you’ll need to make a ‘balancing payment’ to make up the difference.
Deadline for making amendments: If there’s an error on your tax return, you can change it up to 12 months after the 31st January that follows the end of that tax year.