To work out if you’ve paid enough tax to cover your donations, divide the donation value by four.
For example, if you give £100 in a particular tax year you will need to have paid £25 tax over that period. (£100/4 = £25). (Note that this calculation is based on the basic rate tax of 20 per cent).
If you don’t think you’ve paid enough tax this year, you may be able to carry back your donation to the previous tax year.