PLEASE NOTE: The charity TaxAid advises only those people on low incomes whose problems cannot be resolved with HMRC.

How will I know what tax to pay?

Help with your Tax Return guide


If you submit your tax return on-line, then your income tax (and, for the self-employed, your class 4 National Insurance bill) will be calculated automatically. This happens just before you submit the return on-line to HMRC. It is a good idea to check that the calculation is reasonable before you submit the tax return.  If the result of the calculation –  a bill or a refund – is unexpected, then there could be a mistake on your return. You should check all the entries in detail.

Possible errors might include, for example:

If you submit your tax return on paper (due by 31 October), then HMRC should calculate the tax due and send you a calculation in time for the 31 January payment deadline.  You should check this calculation in the same way as for an on-line calculation.

There is more about how tax bills are worked out in the income tax section, where there is a worked example.


Construction Industry Scheme
Year end statement from your employer of gross income and tax paid