What Is an Overdraft and When Is It Worth Using?
Overdrafts sit in a strange position in personal finance: widely used, often misunderstood, and frequently more expensive than people realise. Understanding exactly how the interest works — and when an overdraft actually makes financial sense versus when it's a sign of a problem — is genuinely usefu
⚡ Quick Answer
An overdraft is a short-term credit facility attached to your current account allowing you to spend more than your balance. Arranged overdrafts (agreed in advance) are more expensive than they look: typical rates are 19-40% EAR. Interest is charged daily only on the amount you’ve actually borrowed. Overdrafts work best as genuine short-term buffers (a few days between pay-dates). They’re expensive for anything sustained — a persistent overdraft can build up substantial interest over a year; the cost depends on your daily balance, the rate and any interest-free allowance, but longer-term reliance on overdrafts typically indicates a cashflow problem that a budget review would address better.
Overdrafts sit in a strange position in personal finance: widely used, often misunderstood, and frequently more expensive than people realise. Understanding exactly how the interest works — and when an overdraft (OD) actually makes financial sense versus when it’s a sign of a problem — is genuinely useful.
How Overdraft Interest Is Charged
Following FCA rule changes in 2020, all OD interest must be expressed as an annual EAR (Effective Annual Rate), with no daily or monthly fixed fees. This made OD costs easier to compare but didn’t make them cheaper.
Interest depends on the amount borrowed each day, the bank’s daily rate and any interest-free buffer. EAR includes compounding, so dividing EAR by 365 is not the same as using the bank’s daily interest rate. Use your provider’s overdraft calculator or tariff for a cost estimate. For an independent explanation of borrowing costs and support, see MoneyHelper’s overdraft guide.
Short-duration, small-amount use is not catastrophically expensive. Long-duration or large-amount use is.
Arranged vs Unarranged Overdrafts
Arranged overdraft: agreed in advance with the bank, up to a set limit, at a known EAR. The standard way to use an overdraft.
Unarranged overdraft: going below zero without a pre-agreed facility, or exceeding your arranged limit. Since 2020, banks charge the same EAR as arranged overdrafts — the old punitive daily charges were banned. However, repeated unarranged OD use is damaging to your credit file and may result in the bank closing your account.
When an Overdraft Makes Sense
Genuine short-term timing mismatches — for example, a major bill falls due 4 days before payday and your emergency fund is genuinely not appropriate for this (it’s for real emergencies, not predictable cashflow gaps). A few days’ overdraft use costs very little in absolute terms.
When it’s not a good use:
- Running a persistent month-end OD — this isn’t a timing issue; it’s a spending-exceeds-income issue
- Treating the OD limit as available spending money rather than a safety net
- Using OD instead of an emergency fund — overdraft interest compounds; your emergency fund sits ready at no cost
If you regularly end up in your OD, the underlying issue is almost always cashflow — our guide on creating a monthly budget addresses the root cause more effectively than managing the overdraft itself.
Frequently Asked Questions
Does using an arranged overdraft affect my credit score?
Light use within an arranged limit has minimal credit score impact. Heavy, persistent use signals financial stress to lenders reviewing your file. Unarranged OD use is more damaging. Multiple declined transactions due to insufficient funds also appear in bank data.
Is there a 0% overdraft buffer anywhere?
First Direct offers a £250 interest-free OD buffer on its 1st Account — one of the few remaining examples after the FCA reforms removed most free OD buffers. Student current accounts from major banks also typically include interest-free overdrafts up to a set limit.
For current overdraft rates and comparisons, Which?’s overdraft comparison is regularly updated.
