Short answer: Gift Aid lets a charity reclaim the basic-rate tax you already paid on your income, adding 25p for every £1 your donated item sells for — at zero extra cost to you.
When you donate an item, the shop doesn't just give it away — it sells it on your behalf, as your agent. If you've signed a Gift Aid declaration, the sale is treated as if you donated the cash yourself, and the charity can reclaim the tax on it from HMRC. A £10 jumper sale becomes worth £12.50 to the charity.
No. The extra 25% comes from the tax system, not your pocket. The only requirement is that you're a UK taxpayer for that tax year. Look for the 🎁 Gift Aid tag on shop listings in our directory to see which of your local shops offer it.
Every Gift Aid declaration includes a condition that's easy to skim past: if you pay less Income Tax or Capital Gains Tax in a tax year than the total Gift Aid being claimed on your donations, HMRC can ask you personally to pay the shortfall. This matters if your income drops significantly, you retire, or you stop being a UK taxpayer partway through the year — it's worth telling the shop to update or cancel your declaration if your situation changes, rather than assuming it'll sort itself out.
Gift Aid on donated goods only works if the items genuinely belong to you — legally, you remain the owner until the shop sells them on your behalf as your agent. This catches people out during a house clearance or when donating for someone else: if the items belonged to another person (a parent, a late relative's estate), it's their Gift Aid declaration that would apply, not yours, even if you're the one carrying the bags in.