Calculator
ISA tax-saving calculator
The ISA wrapper's whole job is to shelter your returns from tax. See roughly how much that is worth on a given amount and rate, compared with holding the same investment outside an ISA.
Last reviewed May 2026 · by Gareth Hoyle
What the ISA wrapper saves you
Annual interest
£700
Tax if held outside an ISA
£0
Tax saved by the ISA
£0
Outside an ISA, P2P interest counts as savings income. We apply the Personal Savings Allowance (£1,000 for your band) unless you tick the box above. Inside an ISA the interest is tax-free, so the tax saved equals the tax you'd otherwise pay. Illustrative only, based on 2026/27 bands, and it ignores any interaction with other income. Not tax advice.
How this works
Interest from peer-to-peer lending is treated as savings income. Held outside an ISA, it can be taxed at your marginal rate once you exceed your Personal Savings Allowance (£1,000 for basic-rate, £500 for higher-rate and £0 for additional-rate taxpayers). Held inside an ISA, it is tax-free, so the tax saved is the tax you would otherwise have paid. Remember the wrapper changes the tax, not the risk: your capital is still at risk.
Keep reading
P2P income calculator
Estimate the monthly and annual income a P2P ISA could produce at a given rate, and see how assumed bad debt changes it. Illustrative only.
The £20,000 ISA allowance
How the annual ISA allowance works, splitting it across ISA types, and the rules that catch people out.
Peer to peer ISA FAQs
Straight answers to the most common questions about Innovative Finance ISAs: tax, risk, transfers, allowances and access.