Arranged overdraft interest: how the cost works

Arranged overdraft interest depends on how much of the agreed facility you use and for how long. Banks quote an annual rate, but the charge is generated from the debit balance over the days you remain overdrawn.

An overdraft limit is not a flat-fee product

If your limit is £1,000 but you use only £200, interest is normally based on the amount actually overdrawn, not the full facility. And if salary clears the overdraft after five days, you do not pay as if you borrowed for a month.

That is why two customers with the same £1,000 limit can pay very different interest.

Start with a dated baseline. Check the arranged overdraft rate shown for your account, any interest-free buffer and the balance you expect to borrow each day. The approved limit is not the cost; the cost depends on how much of it you actually use and for how long.

For arranged overdraft interest: how the cost works, cross-check the expected result against the actual result in the section 'An overdraft limit is not a flat-fee product'.

For this part of Arranged overdraft interest: how the cost works, avoid acting from memory. Under “An overdraft limit is not a flat-fee product”, keep the live provider wording beside your own amount, date or account status. If the two do not match, resolve that discrepancy first instead of repeating the payment, application or support request.

A simple estimate makes the annual rate understandable

At 39.9% per year, borrowing £500 for seven days gives a rough simple-interest estimate of £500 × 39.9% × 7/365 = about £3.83. Borrowing the same £500 for 30 days is roughly £16.40. The bank's exact calculation depends on its daily balance and compounding method.

Use the example for scale, then check the actual statement. If your account has a £25 interest-free buffer, only the amount above that buffer should attract interest under the stated terms.

Worked example: compare two patterns with the bank calculator: £500 overdrawn for three days versus £500 overdrawn for thirty days. The same limit can produce very different interest because time in the overdraft matters as much as the peak balance. That is more useful than asking whether the product or process is good in general.

Apply “A simple estimate makes the annual rate understandable” to Arranged overdraft interest: how the cost works with one simple record: the current bank rule, your account-specific fact and the next action that follows from them. If the bank later gives a different answer, you can compare like with like instead of starting the investigation again.

FCA rules require simpler, comparable pricing

The FCA's overdraft rules require charges to be expressed as an annual interest rate and generally stop fixed borrowing fees for personal current-account overdrafts. The rate for an unarranged overdraft also cannot exceed the relevant arranged rate.

Banks can offer different rates to different customers or products, so do not assume 39.9% is universal. Read your own account tariff.

Use a fixed sequence rather than repeated trial and error. track the daily balance around salary, Direct Debits and card settlements, then use the provider calculator or statement to check the interest charged. If you can move a bill date or reduce the balance sooner, model the pounds saved before changing anything. After each step, record what changed and what did not.

For arranged overdraft interest: how the cost works, cross-check the expected result against the actual result in the section 'FCA rules require simpler, comparable pricing'.

Daily cash flow matters more than the monthly statement date

If your balance is -£700 on Monday, -£100 after a transfer on Tuesday and positive on Wednesday, the interest reflects that changing use. Moving spare money into the current account sooner can reduce interest even if you intend to spend it later in the month.

Set balance alerts around zero and around any fee-free buffer. That turns overdraft management into an active daily decision rather than a surprise at statement time.

Timing can change the outcome. a month-end snapshot can hide repeated overdraft use during the month. Review the balance by day, especially around large bills, because a salary credit that clears the overdraft for one day does not necessarily mean the borrowing pattern is sustainable.

Use “Daily cash flow matters more than the monthly statement date” as a decision checkpoint on Arranged overdraft interest: how the cost works. Save the current screen, statement or tariff that supports your conclusion, and note what result would make you stop, contact the bank or choose a different route. That keeps the next step evidence-led.

Persistent overdraft use deserves a bigger fix

If you spend most of each month overdrawn, the overdraft is functioning like long-term debt. Add up three months of interest and compare alternative ways to clear it, but avoid replacing it with more expensive high-cost credit.

Tell the bank if you are struggling. Forbearance can include reducing or waiving charges in appropriate circumstances, and early contact gives more options than waiting for missed payments.

If the normal route fails, switch from retrying to evidence. if the interest looks wrong, ask the bank for the rate, balance period and any buffer used in the calculation. Keep the statement and tariff that applied to those dates so the disputed amount can be checked rather than estimated.

For Arranged overdraft interest: how the cost works, turn “Persistent overdraft use deserves a bigger fix” into one verifiable fact rather than a general impression. Record the amount, status, date or rule that matters, then compare it with the bank’s current information before you make the next transaction or account decision for “Persistent overdraft use deserves a bigger fix” on Arranged overdraft interest: how the cost works.

A free buffer changes the arithmetic materially

Some accounts include an interest-free amount. If the first £250 is free and you are £400 overdrawn, interest may apply only to £150 under the account terms. That makes copying another bank's online overdraft calculator unreliable unless the products have the same buffer and rate.

Use your own tariff and statements. If the bank changes the rate or buffer, note the effective date so you can separate old and new charging periods.

Use one closing decision rule. if arranged overdraft use becomes routine, solve the cash-flow problem rather than only optimising the interest calculation. A cheaper borrowing structure or spending change may matter more than shaving a few days from a persistent overdraft.

Sources and verification

• FCA Handbook - Overdraft pricing
• MoneyHelper - Overdrafts explained

MyBankAnswers uses official provider and UK regulatory sources wherever practical. Information is general and does not constitute financial advice.