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If you fulfil the self-assessment criteria set out by HM Revenue & Customs (HMRC), you will be notified by them that you need to fill in a self-assessment tax return, usually in April. If you believe that you may have to fill in a tax return, you should tell HMRC as soon as you can so that a tax return can be issued to you for completion. A letter will also be issued informing you of the deadline for submitting your tax return.

The deadlines are 31st October for a paper return and 31st January for an online tax return. If you owe less than £3,000 tax, you can ask for this amount to be collected using next year’s tax code. However, if you wish to use this service you must submit your tax return to HMRC by 30th December.

If you submit a paper self-assessment tax return and HMRC calculates your tax bill for you, a form SA302 will be issued. This is a tax calculation and shows details of all income and tax already paid which you have submitted on your tax return.

If you amend your tax return, you will also receive an amended form SA302 which shows the latest figures that you have provided. You will also receive a form SA302 if HMRC disagrees with your tax calculation provided. It is important to check the tax calculation form, as these figures will be used to calculate the tax which is due.

A letter will be issued along with your form SA302 with important information regarding your tax calculation. The letter will state which tax year the calculation is for and the total amount of income tax which is due for that year. The tax figure will have been calculated using the figures that you provided on the self-assessment tax return.

If HMRC has altered any figures on your self-assessment tax return, the letter will give details. If you make ‘payments on account’, the letter will tell you of any that you need to pay in the next year. Payments on account are payments made in advance towards the next year’s tax bill.

If you don’t agree with any aspect of the form SA302 tax calculation, you must contact HMRC as soon as you can so that the figures can be corrected. Any delay in informing HMRC could result in a larger tax bill than actually due, or you paying less tax than you owe. If this happens, you may find yourself with a further tax bill and penalties charged for the amount still owing.

If HMRC doesn’t hear from you, a self-assessment statement will be issued based on the figures in the tax calculation. The self-assessment statement will give details of any tax which is due and needs to be paid, or that a tax refund is due if you have paid too much.

The form SA302 gives you the figure of tax which is due for the year based on the figures that you have provided on your self-assessment tax return. However, you may owe some tax from a previous year or have made a voluntary payment of tax to HMRC. These amounts will be taken into account before your self-assessment statement is issued. However, you need to check the form SA302 and your self-assessment statement carefully to ensure all income and all income tax which has already been paid is accounted for in the calculation.

Other entries may be included on your form SA302, like repayments of a student loan, Capital Gains Tax or, if you are self-employed, you may have National Insurance contributions on the calculation.


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