With a SIPP, the tax main relief you get comes when you actually pay money into it. It sounds strange, but the government actually “tops up” the cash you pay in by the amount of tax you paid on that cash when you earned it.
So, assuming you normally pay tax on your income at 20%, if you paid £80 into your SIPP, HMRC would add another £20 on top – a total of £100 overall. That £20 basically refunds the 20% tax you were charged on £100 of your earnings through the PAYE system or your Self Assessment tax return. Of course, not everyone pays tax at the basic rate. If you’re charged a higher tax rate on some of your income, you can claim the extra 20% or 25% back through a tax return.
You can pay any percentage of your yearly income you want into your SIPP, but there’s a hard limit on the actual tax relief you can get. If you pay more than £40,000 into your SIPP in a year, you won’t get any top-ups from HMRC on anything over that amount. However, if your contributions don’t hit the £40,000 threshold, you can “carry forward” your unused tax relief for up to 3 years, basically stacking it up for future use. You might find this particularly helpful if your earnings tend to change from year to year – if you’re self-employed, for instance. If you can’t save up to the £40,000 threshold in one year, but earn enough to go over it the next, carrying your unused tax relief forward means you don’t miss out.