AER, Gross and Net Savings Interest: A Guide for UK Savers

A UK savings advertisement can show an annual equivalent rate, a gross rate and a reference to tax-free interest on the same screen. These are not three separate bonuses. They describe different aspects of the return. Understanding which question each number answers makes it easier to compare accounts without mistaking an annualised illustration for a guaranteed cash payment.

This guide focuses on the labels and the calculations behind them. It does not rank current accounts or establish your tax liability. Interest rates, access terms and tax rules can change, so keep a copy of the dated account summary and use the rules for the relevant tax year. The worked examples use fictional rates and balances.

Start with AER: the annual comparison measure

AER means annual equivalent rate. NS&I explains the convention in terms of interest being compounded when paid. The label helps express an annual return on a comparable basis when payment intervals differ. It does not mean every saver receives that percentage of the largest balance they held at any point during the year.

Actual interest depends on when money arrives, when it leaves, the rate that applies and whether interest stays in the account. A fixed AER and a variable AER also make different promises about future rates. Read the interest calculation and payment frequency alongside the headline number. A short introductory rate needs particular care because the account may not keep that rate for the whole period you intend to save.

Gross and net answer the tax question

Nationwide’s explanation of savings labels describes gross interest as interest before tax is deducted. A net figure describes what remains after an applicable tax deduction or tax calculation. AER is about annual comparison and compounding; gross or net describes tax treatment. These ideas should not be collapsed into one label.

A gross credit to your account is not proof that the interest is exempt from tax. MoneyHelper explains that savings interest is usually paid gross and that tax-free allowances and reporting arrangements depend on the person’s circumstances. An ordinary savings account and a cash ISA therefore require a comparison of actual terms as well as the advertised rate.

Three labels, three useful questions

Label	What it helps describe	What to verify separately
AER	An annualised comparison that reflects compounding assumptions.	Rate changes, balance timing and account restrictions.
Gross	Interest before tax.	Whether any of your interest is taxable.
Net	Interest after the relevant assumed tax treatment.	The actual allowance and tax rules applying to you.
Tax-free	A tax treatment attached to the qualifying account or interest.	Eligibility, contribution rules, access and other product terms.

See why monthly compounding changes the annual result

Imagine an account pays a fictional nominal gross annual rate of 4%, with one twelfth of that rate applied each month and all interest left in place. Start with £1,000 and make no deposits or withdrawals. The simplified calculation is £1,000 × (1 + 0.04 ÷ 12)¹², producing approximately £1,040.74 before tax.

The resulting annual gain is about 4.074%, rather than exactly 4%, because later months earn interest on earlier interest. This is a teaching model, not a reconstruction of a bank’s daily calculation or rounding. If an actual summary gives both a monthly gross rate and an AER, use its stated convention rather than assuming that the model exactly reproduces every statement.

Now imagine the interest is transferred out each month rather than retained. You no longer earn interest within that account on those withdrawn credits. The account can still display an AER for comparison, but your actual pattern of cash flows differs from the retained-interest example. Ask where the interest goes and whether the payment destination itself earns anything.

Do not apply a full year’s rate to money deposited gradually

A regular saver often receives a sequence of deposits rather than one opening lump sum. Suppose you contribute £100 at the end of each month for twelve months. Your contributions total £1,200, but the final £100 has not been present for twelve months. Multiplying £1,200 by the headline annual rate treats all those deposits as if they arrived together at the start.

Draw a simple timeline instead. Note each deposit date and the period it can earn interest. Then use the provider’s illustration or a calculator that models the same contribution timing. Keep regular-saver limits separate from the interest calculation: an account may restrict monthly deposits, withdrawals, missed payments or eligibility. A high rate on a limited balance is not directly comparable with a rate available on your entire lump sum.

Estimate tax only after identifying the relevant interest

HMRC’s savings-interest guidance explains that the Personal Allowance, starting rate for savings and Personal Savings Allowance may affect how much interest is taxable. Their relevance depends on other income and the applicable tax year. Check the official guidance rather than assuming that every pound of interest is taxed, or that none is.

For a purely hypothetical example, assume an account earns £400 gross, only £200 is taxable after the relevant allowances, and an illustrative 20% tax rate applies to that taxable portion. Tax would be £40 and the retained interest would be £360. This is different from deducting 20% from all £400. The assumptions are invented and do not establish a current tax rate or your eligibility for an allowance.

Use total relevant interest across your accounts when making a personal estimate; do not allocate the same allowance afresh to each bank. Record which tax year the interest belongs to and investigate unusual payment arrangements rather than guessing. A tax adviser or HMRC can help with circumstances outside a simple example, including other income or special account structures.

Compare access and restrictions before choosing the higher rate

Make a shortlist with one row per account and a consistent planned balance. Record whether the rate is fixed or variable, when interest is paid, any minimum or maximum balance, and the rules for withdrawing money. Check what happens at the end of a fixed term or introductory period. The comparison should reflect how you expect to use the money.

Suppose a fictional account earns £30 more interest over your intended period but an early-access charge would cost £75 if you needed the money. That does not mean you will incur the charge; it identifies a trade-off worth discussing before you commit. Keep emergency access needs separate from money you can confidently leave untouched. A higher AER is useful information, but not a complete household decision.

Read the illustration as an illustration

A projected balance can assume a constant rate, no withdrawals and interest remaining invested. Those assumptions should be visible in the account information. Save the illustration with its date so you can distinguish the original terms from a later rate change. If a provider’s figures differ from your calculation, compare payment timing and rounding before concluding that an error has occurred.

The savings growth calculator lets you explore explicit assumptions. It is not a bank statement or a tax calculator. Our APY and APR guide explains related terminology used in other contexts; do not substitute a borrowing APR for a savings AER when comparing UK cash accounts.

A useful record before opening the account

Keep the account name, product version, application date, rate summary and withdrawal rules together. Add your intended deposit schedule and note where interest will be paid. If you need clarification, ask the provider a specific question such as whether the displayed illustration assumes monthly interest stays in the account. This creates a record you can compare with later statements.

Finally, separate the calculation from the product’s broader suitability. Check the institution, eligibility and relevant deposit-protection arrangements through official information, and verify any unexpected message before transferring money. Understanding AER, gross and net should make the comparison clearer; it should not encourage a rushed transfer based on a number copied from an advertisement.

For UK accounts with different tax treatment, compare cash ISAs and ordinary savings accounts alongside the interest figures rather than choosing from the headline rate alone.

Common questions

Does AER mean I receive that percentage every month?

No. AER is an annual comparison measure, not a monthly payout percentage. The actual payment frequency and calculation method appear in the account terms. Check whether interest is paid monthly or annually, whether it remains invested, and whether the rate can change during the period you plan to save.

Why can the gross rate be lower than the AER?

When interest is paid and retained during the year, compounding can make the effective annual return higher than a nominal gross annual rate. The provider’s stated convention matters. Read both labels and the payment schedule instead of assuming that one number is an error or an additional bonus.

Does gross interest mean the account is tax-free?

No. Gross means before tax; it does not by itself establish exemption. Savings interest may be paid without tax being deducted, while tax liability depends on allowances, other income and the relevant year. Use HMRC’s current guidance for your circumstances instead of treating the bank’s credit as a tax decision.

Can I calculate interest by multiplying my final balance by AER?

Only if the assumptions genuinely fit, such as an unchanged opening balance held for a full year under the applicable rate conditions. Money added gradually has different earning periods. Withdrawals and rate changes also matter. Use a dated cash-flow schedule or the provider’s matching illustration for a more realistic comparison.

Does monthly interest always produce a better return?

Not by itself. Compare AER and actual terms, including whether the interest remains invested or is paid elsewhere. Two different payment schedules can produce similar annual results. Access restrictions, balance limits and rate changes may matter more to your situation than the frequency of credits on a statement.

What does net interest depend on?

It depends on the gross interest and the tax treatment that actually applies. A displayed net example may use assumptions that do not match your allowances or income. Keep those assumptions explicit and do not deduct a percentage from every account’s interest without considering the relevant overall tax position.

Is a regular saver comparable with a lump-sum account?

You can compare them, but you need consistent cash-flow assumptions. A regular saver may limit monthly contributions, so its highest balance is not present for the full year. Include where the rest of your money would sit while awaiting each contribution, and read any restrictions on access or eligibility.

Is the highest AER automatically the best choice?

No. It may come with conditions that do not fit your need for access, your balance or your deposit schedule. Compare the additional interest with relevant restrictions and possible charges. This guide provides a calculation framework, not a personalized recommendation or a ranking of current savings products.

Should I use the same tax allowance for each bank?

Do not assume an allowance resets for every institution. Check HMRC’s rules using your relevant total interest and income for the tax year. Keep statements from different providers together so the calculation is not based on only one account. Seek help for circumstances beyond a straightforward illustration.

What should I save from the account information?

Keep the dated rate summary, product name, payment frequency, withdrawal conditions and any illustration assumptions. Note your planned deposit dates and where interest will be credited. Those records make it easier to understand later statements and to ask a precise question if the amounts differ from your expectation.

Sources and references

• NS&I explains the convention Accessed 2026-10-19.
• Nationwide's explanation of savings labels Accessed 2026-10-19.
• MoneyHelper explains Accessed 2026-10-19.
• HMRC's savings-interest guidance Accessed 2026-10-19.