Personal allowance taper and the personal savings allowance
Two rules share this lesson, and they fail in opposite directions, so keep their mechanisms apart from the start. The personal allowance is a DEDUCTION of £12,570 — income it covers leaves the calculation. Its trap is the taper: once adjusted net income passes £100,000, the allowance shrinks by £1 for every £2 of excess, automatically, until it is nil at £125,140. Before the exam shows you a six-figure client, fix two details the taper questions turn on: 'adjusted net income' means income from EVERY source — salary, rental, interest, dividends, including amounts sitting at 0% inside allowances — and the withdrawal is half-speed (£1 per £2), which is what makes the effective marginal rate in the taper zone HIGHER than the headline higher rate: each extra pound is taxed itself AND drags formerly tax-free income into charge. The personal savings allowance is the opposite mechanism: a NIL-RATE BAND, not a deduction. Interest inside it is taxed at 0% but stays in the band stack, still occupies capacity and still counts toward income tests — including the taper test itself. Its trap is the tier structure: £1,000 for basic-rate taxpayers, £500 for higher-rate, and NOTHING for additional-rate — the exam loves a client just over £125,140 still being given the £500 allowance. Deduction that tapers; nil-rate band that tiers. Say it that way and the two rules stop bleeding into each other.
- Excess over the taper threshold
- 110,000 - 100,000 = £10,000
- Allowance reduction: £1 for every £2 of excess
- 10,000 / 2 = £5,000
- Personal allowance after the taper
- 12,570 - 5,000 = £7,570
No election, no warning — the allowance shrinks automatically as adjusted net income crosses the threshold. And because this client is a higher-rate taxpayer, any savings interest they had would get the £500 PSA, not the £1,000 basic-rate figure.