In-depth guide

Compound interest in the UK context: what savers should check

UK banks often quote interest as an annual equivalent rate (AER) for savings. This guide ties that convention to the compound growth intuition you see in our calculator—without pretending to offer regulated financial advice.

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AER and what it captures

AER shows what you would earn if interest were paid annually while preserving monthly compounding effects. It helps compare accounts that credit interest on different schedules.

Sterling example

Imagine £5,000 in a savings account with a stated AER; monthly crediting means interest lands twelve times a year, each time slightly lifting the balance that earns the next slice of interest.

Pitfalls with UK products

Introductory rates, tiered balances, and gross vs net of tax treatment can all move outcomes away from a single headline figure. Use the calculator as a baseline, then read product terms.

FAQ

Is AER the same as APR?
No. APR is widely used for borrowing costs; AER is designed to standardise savings returns. They answer different questions.
Why might my ISA projection differ?
Allowances, subscription timing, provider fees, and changing rates alter realised growth compared with a smooth constant-rate model.
Are returns guaranteed?
No. Market-linked or variable-rate products change over time; models assume stable inputs unless you scenario-test.

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