Tax relief on a charitable gift.

A 1,000 donation by a 40% marginal rate taxpayer under gift aid receives 250 of additional relief on top of the basic-rate gift aid claimed by the charity — bringing the true net cost down to around 750. Understanding this gap lets you be more generous for the same after-tax cost.

What the result means

Relief is the additional tax saving you personally claim — the difference between your marginal rate and the standard tax rate. Net cost is the gross donation less your personal relief. The charity receives the gross plus basic-rate claim regardless.

In systems without gift aid, relief is often a straight itemised deduction at your full marginal rate — use the marginal rate directly as the relief rate.

Run it with sensible defaults

Using gross donation of 1,000, marginal tax rate of 40%, basic/standard rate of 20%, the calculation works out to 250.00. Nudge the inputs toward your own situation and the output recalculates instantly. The defaults are meant as a starting point, not a recommendation.

The levers in this calculation

The inputs — Gross Donation, Marginal Tax Rate, and Basic/Standard Rate — do not pull with equal force. Not every input has equal weight. Flip one at a time toward extreme values to feel which ones move the needle most for your situation.

How the math works

Personal relief under a gift-aid-style system equals the donation times the difference between marginal and basic rates divided by one minus the standard tax rate. In a pure deduction system, set standard rate to zero — relief then equals donation times marginal rate. The working is transparent — you can verify every step yourself in the formula section below. No black box, no opaque "proprietary model".

Using this in pay negotiations

Knowing the exact figure behind a headline rate gives you specific numbers to anchor to in conversations about pay. "The difference is £X per month after tax" lands harder than "a couple of grand a year". Concrete numbers move decisions.

What this doesn't capture

Tax bands, pension contributions, student-loan deductions, and benefits-in-kind sit outside this calculation. The figure is the headline; your actual position depends on local tax rules and personal circumstances. Pair with a dedicated take-home calculator for the full picture.