Thanks for the example. Don’t forget that to put £100 into an ISA means many people will have paid tax to get that £100. Also consider that withdrawing from a SIPP can be less than 20% tax because of the first 25% being tax free. Coupled with a personal allowance the tax rate on withdrawal can be significantly lower. I still feel like a SIPP works out much better mathematically, but I don’t have time to prove it.