With Gift Aid, your generous donation of £10 would be worth £12.50 at no extra cost to you.
I am a UK taxpayer and I understand that if I pay less Income and /or Capital Gains Tax than the amount of Gift Aid claimed on all my donations in the relevant tax year, it is my responsibility to pay any difference.
In our 35th year we’re asking people to donate £35 – that’s just £1 for every year we’ve been providing life-changing information. Any donation you make helps us continue our work towards a world where HIV is no longer a threat to health or happiness.
UNAIDS 
ViiV Healthcare press release
Huffington Post (blog)
HepCoalition
NPR
TB Europe Coalition