Do you need to file for self-assessment? Put these deadlines in your diary

The first in a string of deadlines for self-assessment tax returns falls on 5 October and this and the key dates which follow it are important. Knowing which ones apply to you can help you avoid a big fine in the future.

Some filing self-assessments may have completed the process much earlier this year, but it can be an easy thing to put off until the last minute. To make sure last minute doesn’t turn into too late, let’s examine the upcoming dates. First though, it is worth determining if it’s something that needs to be on your radar at all.

Do I need to file for self-assessment?

People often associate self-assessment with being self-employed. But there are other cases where filing could be necessary, like if you rent out a property or do trade work. You can find out if your situation requires you to file by taking a questionnaire. If you do find that you need to file, you can estimate what you will need to pay with the Self Assessment tax calculator calculator.

One of the main reasons that investors may need to file is dividend payments from their investments. For the 2024/25 tax year, there is a dividend allowance of £500 which will not be subject to tax. However, any dividends you are paid that exceed that amount are classified as income and will need to be recorded with HMRC. If the amount paid out in dividends is below £10,000, you will just need to contact HMRC so they can adjust your tax code. This needs to be done before the end of 5 October. If it is more than £10,000, you’ll need to file a self-assessment tax return.

Registering for self-assessment

If you are filing a self-assessment tax return for the first time, or if you didn’t file a self-assessment return last tax year even though you have previously, you will first need to register. This needs to be completed by the end of 5 October, or you could get a penalty for being late. Once you’ve registered, HMRC will send you a letter, called a notice to file. You’ll need to file the return by 31 January, or three months after the date of the letter, whichever one comes later.

Sending your return

Once registered, you’ll need to send your return. This can be done in paper or online, but if you file by paper, it must be received by HMRC by 31 October, or you could get a penalty.

The deadline for those filing online is 31 January (for the tax year before). However, if you plan to pay your self-assessment bill through your tax code, you need to submit the return by 30 December.

How much do you need to pay?

HMRC will use your self-assessment return not only to establish what you need to pay for this year, but to assume what you will owe next year. If your self-assessment tax bill is less than £1,000, you’ll just need to pay by 31 January and will then be set until the next year.

You will also just need to handle your bill by 31 January if more than 80% of your tax was deducted at source, through something like PAYE. This usually applies to those who are otherwise employed and earning some money through their investments on top.

But, if you don’t fall into either of these categories, you’ll be using the payments on account system. This means that HMRC will start estimating what tax you owe for the next year and billing you for that as well. If it’s your first year of paying tax, you’ll pay your entire tax bill for the previous year by 31 January.

You’ll need to be ready to pay half of that tax bill again by 31 July. This will count as a payment for the following tax year, and then you’ll pay whatever is leftover once you do your return by the next 31 January. So, after that first year, you’ll pay about half of your tax bill in July and the other half in January.

Paying the bill

Once the return is submitted, you’ll need to pay any tax you owe. Note that this is due the same day as your return, 31 January. There are lots of different ways that you can pay, but it’s important to keep in mind how long it will take the payment to go through, so you aren’t hit with fines.

If 31 January does not fall on a working day, you need to make sure the payment goes through by the last working day before it. Some ways you can pay same or next day include through your online bank account, through a debit or corporate credit card, at your bank (with a paying-in slip), or with CHAPS.

If you choose a method like Bacs, direct debit, or cheque through the post, it could take closer to three to five working days.