If you give money to charity then you can obtain tax relief if you are a higher rate taxpayer and the donation was made to a registered charity in the EU (plus Norway, Iceland and Liechtenstein).
You can also obtain relief for donations made to Community Amateur Sports Clubs (CASCs) that were registered with HMRC when you made the donation.
You’ll need to make a gift aid declaration to the charity, whether its in writing/electronic/verbal and you should also receive and keep a receipt for the donation.
Your basic rate limit will be increased by the donation, grossed up by the basic rate 20%, and this means that you will save tax.
For example, if you give £1,000 to charity and are a 40% taxpayer, your basic rate will be increased by £1,000 x 100/80 = £1,250. The tax saving is then £1,250 x (40%-20%) = £250
Carry back to previous tax return
You can claim gift aid early by including it in your previous tax return upto 31 January.
For example, you make a donation in October 2017, and you can claim it in the 2016/17 tax return is due by 31 January 2018 (instead of waiting until the following year for 2017/18 tax return).
There are sometimes reliefs available, but you should check the rules