Why the headline rate is only the beginning

When you look at a savings table, your eye goes straight to the biggest number. That is only natural. But a headline rate on its own can flatter an account that does not really suit you. Two accounts can both advertise 4.5% and behave completely differently the moment you try to use them. One might let you move your money out whenever you like, while the other locks it away for two years or asks for 90 days' warning before a withdrawal. Learning to read what sits behind the number is the most useful savings skill there is, and it takes far less time to pick up than most people expect.

What AER actually means

AER stands for Annual Equivalent Rate. It is the rate you would earn over a year if you left all the interest in the account to compound. That last part matters. If an account pays interest monthly and you leave it alone, the monthly interest starts earning interest too, so your money grows slightly faster than the gross rate suggests. The AER bakes that in, which is why it is the fairest figure for comparing one account with another.

Where people get caught out is assuming AER is the same as what lands in their pocket. Two things can reduce it:

• If you take the interest out each month rather than leaving it to compound, you receive the gross rate instead.
• Savings interest counts as taxable income. Most people have a Personal Savings Allowance — £1,000 a year for basic rate taxpayers, £500 for higher rate, and nothing for additional rate taxpayers. Go above it and you will owe tax on the excess, unless the money sits in a cash ISA, where the £20,000 annual allowance shelters it completely.

Variable rates, bonuses and the loyalty trap

Many of the best-looking accounts are variable rate deals with an introductory bonus. The bonus might run for twelve months and then vanish, dropping the rate to something unremarkable. Others are simply variable, which means they can move whenever the provider chooses — and providers tend to pass on cuts faster than they pass on rises.

This creates the loyalty penalty. Customers who leave money sitting in the same account for years often end up on a rate that is a fraction of what is available to new customers. It is not personal, and it is not illegal. It is just how the market works, which is why the date you opened an account matters as much as the rate on it.

• Note the date any bonus period ends and put a reminder in your diary.
• Check the rate on every savings account you hold at least twice a year.
• If an account has slipped behind, move it — switching is usually a few minutes' work.

Notice periods and fixed terms: the trade-off

Notice accounts ask you to give advance warning — often 30, 60 or 90 days — before you withdraw. In return you usually get a better rate than an easy access account. Withdraw early without giving notice and you will typically lose some interest, or pay a charge.

Fixed rate bonds go further. You agree to leave your money in for a set term, commonly one to five years. The rate is locked, which is genuinely valuable when rates are falling. But access is restricted: some bonds allow no withdrawals at all, while others allow early closure only with a penalty equivalent to several months' interest.

The sensible question is not "which pays most?" but "when might I need this money?" Money you may need at short notice belongs in an easy access account, even at a lower rate. Money you are confident you will not touch can be fixed. Some savers split the difference by laddering: putting equal sums into one, two and three year bonds, so something matures regularly and you are never far from access.

Comparing accounts without getting lost

Work through the same short list every time you look at a new account:

• AER — the rate that lets you compare fairly.
• Access — easy access, notice, or fixed?
• Minimum deposit — some accounts need £1,000 or more just to open.
• Withdrawal rules — how many free withdrawals, and what happens if you exceed them?
• Regular saver limits — a headline 6% on a regular saver that accepts £200 a month is not 6% on a £2,400 pot. You only earn the top rate on money once it is in, so the real return on the full sum is roughly half the advertised figure.

Building habits that keep your cash working

Start with an emergency fund — three to six months of essential spending — in an easy access account you can reach the same day. Everything beyond that can be organised deliberately.

Then set a simple routine. Review your accounts every six months, perhaps when the clocks change. Move any bonus-period money out before the rate drops. Keep a rough tally of your annual interest so you know whether you are approaching your Personal Savings Allowance, and use a cash ISA if you are. And remember that a slightly lower rate on an account you will actually manage beats a headline rate on one you forget about. Small, regular attention is what keeps your savings earning properly.