How Credit Card Interest Builds Up — Daily Rates, the Minimum Payment Trap & the Real Cost
Updated May 2026 · UK credit cards 2026/27 · 9 min read
How daily interest is calculated
Unlike personal loans — which charge interest monthly on the opening balance — most UK credit cards charge interest daily on the outstanding balance. Here's the mechanics:
Daily rate = APR ÷ 365
Each day, interest is calculated on the current balance and added to a running total
At the end of your statement period, all the daily interest charges are summed and added to your balance
Daily rate calculation for a 24.9% APR card
Daily rate: 24.9% ÷ 365 = 0.06822% per day
On a £3,000 balance:
Day 1 interest: £3,000 × 0.0006822 = £2.05
Monthly interest (30 days): approximately £61.35
Annual interest (if balance unchanged): approximately £747
On a £3,000 balance at 24.9% APR, you're paying over £60/month just to stand still — before any principal reduction.
APR vs EAR — what's the difference?
APR is the simple annual rate. EAR (Effective Annual Rate) accounts for daily compounding — which means the true annual cost is slightly higher than the stated APR. For most practical purposes, the difference is small, but it explains why the actual interest charged can exceed APR ÷ 12 each month.
What common APRs actually cost per month
Here's what different APRs cost in monthly interest on common balance sizes — assuming no payment is made that month:
Balance
19.9% APR
24.9% APR
34.9% APR
49.9% APR
£500
£8.29
£10.38
£14.54
£20.79
£1,500
£24.88
£31.13
£43.63
£62.38
£3,500
£58.04
£72.63
£101.79
£145.54
£5,000
£82.92
£103.75
£145.42
£207.92
£8,000
£132.67
£166.00
£232.67
£332.67
These figures assume no transactions or payments. In practice, your interest charge appears on your statement once a month and compounds if unpaid.
The minimum payment trap — explained
The minimum payment trap is one of the most damaging features of UK credit card debt. It's designed — intentionally or not — to keep you in debt for as long as possible.
How minimum payments are calculated
UK credit card minimum payments are typically the higher of:
A fixed floor amount (usually £25 or £35)
1% of the outstanding balance plus that month's interest
The crucial detail: as your balance falls, so does the minimum payment. When your balance is £3,500, you might pay £87. When it's £500, the minimum is only £30. When it's £200, it might be £27. You're paying just enough to slightly reduce the balance — but the debt barely shrinks.
The real cost of minimum payments on £3,500 at 24.9% APR
Paying minimums only: takes approximately 200 months (16.7 years) to clear. Total interest paid: approximately £6,130. You repay nearly three times the original balance.
The reason it takes so long: as the balance slowly falls, the minimum payment falls too — creating a self-perpetuating system where you're always paying just above the interest charge, with only a tiny slice clearing actual debt.
Fixed payment vs minimum — the difference is enormous
The single most impactful thing you can do with credit card debt is switch from minimum payments to a fixed amount and never let that payment reduce as the balance falls.
Minimum payments only
Balance: £3,500 at 24.9% APR
First payment: ~£87/month
Last payment: ~£25/month
Time to clear: 200 months (16.7 years)
Total interest: £6,130
Total paid: £9,630
Fixed £100/month
Balance: £3,500 at 24.9% APR
Every payment: £100/month
Last payment: still £100
Time to clear: 64 months (5.3 years)
Total interest: £2,808
Interest saved: £3,322
Fixing your payment at £100 — barely more than the first minimum — saves over £3,300 in interest and clears the debt 11 years earlier. This is the single most powerful debt reduction action available at no extra cash cost.
Set a fixed direct debit above the minimum today
Log into your bank or card account and set a direct debit for a fixed amount — not the minimum payment option. Even £10 more per month than the minimum compounds into significant savings over time. Use our Credit Card Repayment Calculator to see the exact saving for your balance.
How 0% balance transfers work
A 0% balance transfer card lets you move existing credit card debt to a new card and pay 0% interest for a promotional period — typically 12 to 30 months in 2026. During this period, every payment you make goes directly to reducing the debt.
The key terms to check
Transfer fee: Usually 2%–3% of the balance. On a £3,500 balance, a 3% fee costs £105. This is almost always worthwhile if you'll save more in interest.
Promotional period length: How many months at 0%? Enough to realistically clear the balance?
Revert rate: What APR kicks in after the promotional period? If you don't clear the full balance, you'll revert to this rate — often 20%–30%.
Minimum payment rule: Missing even one payment usually immediately voids the 0% offer. Set up a direct debit for at least the minimum on the day the account opens.
0% balance transfer — worked example
Sophie has £3,500 at 24.9% APR. She transfers to a 0% card for 24 months, 2.9% fee.
Transfer fee: £3,500 × 2.9% = £101.50
New balance to clear: £3,601.50
Monthly payment to clear in 24 months: £150.06/month
Total interest on 0% card: £0
vs staying on old card at £100/month: £2,808 interest over 64 months
Sophie pays £101.50 to transfer and clears the debt 40 months earlier with zero interest — saving over £2,700. The balance transfer is overwhelmingly worth it.
Don't use the new card for purchases
Most 0% balance transfer cards charge standard APR on new purchases immediately. Using the card for spending while repaying a balance is complex and expensive — keep the new card solely for paying down the transferred balance.
Cash advances — the hidden danger
Taking cash from an ATM using your credit card is a cash advance — and it is treated very differently from regular purchases:
No interest-free period: Interest starts accruing from the moment you withdraw — even if you pay your full balance the same day
Higher APR: Most cards charge a separate, higher APR for cash advances — often 5%–10% above the purchase rate
Cash advance fee: Usually 2%–3% of the withdrawal (minimum £3–£5), charged upfront
Payment allocation: Under FCA rules since 2011, extra payments above the minimum must be applied to the most expensive debt first — but minimum payments go to cheaper balances first
Avoid cash advances on credit cards entirely unless in genuine emergency. Even a small withdrawal at 29.9% APR with a 3% fee costs more than most payday loan scenarios at low amounts.
FCA rules protecting UK cardholders
Since 2011 and updated in 2021, the FCA has introduced significant protections for credit card customers:
Payment allocation: Payments above the minimum must go to the most expensive debt first (e.g. cash advance balance before purchase balance)
Minimum payment warnings: Your statement must show how long minimum-only payments will take and the total interest cost
Persistent debt intervention: Customers who make only minimum payments for 36 consecutive months must be contacted and offered an affordable repayment plan. If no plan is agreed, the lender may be required to suspend interest and fees
Credit limit increases: Lenders cannot increase your credit limit without your explicit consent
Section 75 protection: Purchases between £100 and £30,000 are jointly liable with the lender if the retailer fails to deliver or goes bust — a powerful consumer protection not available on debit cards
See exactly what your credit card debt is costing
Enter your balance and APR to compare minimum payments vs a fixed amount — and see the exact interest saving.
Example 1 — Sophie: The minimum payment wake-up call
Sophie has a £3,500 balance at 24.9% APR and has been paying the minimum for two years.
Balance after 2 years of minimums: approximately £2,870 (barely moved)
Interest paid so far: approximately £1,370
If she continues on minimums: another 14 years and £4,760 in interest
Sophie switches to a fixed £150/month. She'll clear the £2,870 remaining in 25 months and save approximately £2,400 in interest from today. Or she transfers to a 0% card and clears it in 19 months with zero further interest.
Example 2 — Raj: High-rate store card
Raj has a £1,800 store card balance at 39.9% APR.
Monthly interest at current balance: £59.85/month
Minimum payment (month 1): approximately £43 (less than the interest — balance growing!)
Time on minimums only: 13+ years, £4,600+ in interest
Raj's minimum payment doesn't even cover the monthly interest — his balance is growing. He needs to pay at least £60/month to stop the balance rising, and ideally £120+/month to clear it in under 2 years.
Example 3 — Priya: Smart credit card use
Priya puts all her spending on a cashback credit card at 24.9% APR and pays the full balance every month.
Average monthly spend: £1,400
Interest paid: £0 (full balance cleared each month)
Cashback earned: 1% = £168/year
Section 75 protection on all purchases above £100
Priya pays no interest and earns £168/year in cashback. The high APR is irrelevant because she never carries a balance. This is the optimal credit card strategy — only possible with reliable monthly full repayment.
Frequently Asked Questions
How is credit card interest calculated in the UK?
Credit card interest is calculated daily on the outstanding balance. The daily rate is your APR divided by 365. At the end of each statement period, all the daily interest charges are summed to create your monthly interest charge. For a £3,000 balance at 24.9% APR, the daily cost is approximately £2.05, adding up to roughly £62 per month.
What is the minimum payment on a credit card?
UK credit card minimums are typically the higher of: a fixed floor (usually £25–£35), or 1% of the outstanding balance plus that month's interest. As your balance falls, so does the minimum — which is why minimum-only payments keep you in debt for over a decade on typical balances. Always pay more than the minimum if you can.
Do credit cards charge interest if I pay in full each month?
No. Paying your full statement balance by the due date gives you an interest-free period — typically 45–56 days. Interest only accrues when you carry a balance. Cash advances are the exception — they attract interest from the moment of withdrawal, even if you clear the full balance the same day.
How does a 0% balance transfer work?
A 0% balance transfer moves existing debt to a new card charging 0% for a promotional period (12–30 months typically). You pay a transfer fee of 2%–3%. During the 0% period, every payment clears principal. Set up a direct debit for at least the minimum immediately — missing one payment usually voids the 0% deal and reverts to the full standard APR immediately.
What are the FCA rules on credit card minimum payments?
Since 2021, lenders must contact customers making minimum payments for 36+ consecutive months and offer an affordable repayment plan. Your statement must show total interest and time to repay on minimums. Payments above the minimum must be applied to the most expensive debt first. Lenders cannot increase your credit limit without your explicit consent.