How this article was researched

Primary guidance and, where named, a dated issuer example support a distinct reader decision. Calculations are labelled illustrations; there is no universal product ranking or personalised recommendation.

Commercial status: There are no affiliate links in this edition. Providers did not pay for inclusion or approve this copy.

A balance transfer saves money only when two repayment schedules show it. The headline rate cannot answer that question. Your current card balance, actual rate, transfer fee, approved amount and repeatable payment do.

Build both schedules to the same date and with the same monthly payment. That single discipline stops a larger payment, an unfinished balance or a market average from being mistaken for savings created by the transfer.

Use the market rate as context, not an input

The Bank of England's 29 September 2026 release reported that the effective rate on interest-charging UK credit cards rose to 21.55% in August. That is measured market data. It is not an advertised offer, representative APR or personal rate, so do not paste it into your calculation unless it actually matches the rate in your own documents.

Take the rate, balance and payment date from your statement or agreement. Label whether a figure is monthly, annual or APR. If the account separates purchases, transferred balances or cash transactions, keep them separate; a single blended number can hide a category charged differently.

Your first evidence row should read: opening balance, applicable rate, planned payment and calculation date. Add any existing promotion or fee. Mark an unclear rate “unconfirmed” and ask the issuer rather than filling the gap with a comparison-site number.

Build the stay-put schedule

For a simple monthly estimate, calculate interest on the opening balance, add that interest and subtract the payment. Carry the closing balance to the next row. Cap the final payment at the amount owed. Real cards can use daily balances and different timing, so label this a planning estimate.

Use an invented example to check the method: £3,000 at 2% per month, £200 paid at each month-end, no new spending or fees. Month one adds £60 interest and leaves £2,860 after payment. Month two adds £57.20 and leaves £2,717.20.

Continuing the same recurrence clears the illustrative balance in month 19. The last payment is about £2.32 and total payments are about £3,602.32, including about £602.32 of interest. These are recalculated example results, not a quote, typical borrower outcome or forecast for your account.

Build the transfer schedule with the fee included

Checked on 9 October 2026, TSB advertised up to 38 months at 0% on balance transfers and a 3.49% fee for transfers made in the first 90 days. It says the credit limit, promotional period and rates vary with circumstances. This is a dated issuer example, not a ranking or prediction of your offer.

In the invented £3,000 example, a 3.49% fee is £104.70. If that fee is added to the transferred balance and the full £3,104.70 remains at 0% until cleared, £200 monthly payments finish in month 16: fifteen payments of £200 and a final £104.70.

Against the invented stay-put schedule, financing cost falls by about £497.62. That difference is conditional on the same payment, a full transfer, unchanged 0% treatment and no further charges or spending. If any condition changes, recompute both schedules rather than carrying the savings figure forward.

Make the comparison fair

Use the same decision horizon. A transfer plan with debt remaining at the end is not cheaper merely because the spreadsheet stops. Show total payments, interest, fees and closing balance at the chosen date. Where debt survives the promotion, continue with the actual later rate from the offer.

Use the same payment in both plans to isolate the financing terms. If you can pay more, run a second pair of schedules with that larger amount. Otherwise a transfer can receive credit for savings that really came from a higher payment.

For a partial approval, split the debt into two schedules: the amount moved and the amount left behind. Include both required payments. Keep the old account visible until the providers confirm the transfer and the remaining balance.

Test the conditions that can reverse the result

MoneyHelper says transfer fees are commonly added to the statement balance, purchases may have a different rate, and the amount transferable depends on the individual limit. It also warns against assuming another balance-transfer offer will be available later.

Run a weaker-income version of the payment plan. Include any overlap while the transfer is processing and the old card still requires attention. The calculator assumes payments happen; it cannot make an unaffordable payment sustainable or replace the minimum required by the agreement.

Keep new spending at zero in the comparison unless you add the same clearly labelled transactions to the relevant plan. An interest-free transfer does not establish that purchases are interest-free, and a purchase offer does not automatically cover transferred debt.

Turn the result into a decision record

Save the two schedules with their source documents and calculation date. Put the result into one sentence: “Under these inputs, plan A costs £X less by date Y and leaves balance Z.” Then list the unconfirmed conditions directly below it.

If the transfer plan fits and the actual offer confirms the inputs, investigate it further. If the current card clears sooner or more cheaply, keep the workable stay-put plan. If neither payment fits after essentials, contact the provider and use a verified free debt-advice route instead of treating another application as the solution.

The final check is deliberately plain: same debt, same payment, same date, all fees included. A savings claim that cannot survive those four controls is not ready to guide an application.

From comparison to calculation

Check the terms in the offer you actually receive.

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Primary sources and product pages

Product details last checked Oct 9, 2026; next scheduled review Nov 4, 2026. This UK-focused guide is educational information, not individualized financial, legal or tax advice. Product terms, offers and eligibility can change.