Carrying a balance on a credit card can be an expensive way to borrow. The potential costs are even greater for those who struggle with debt, have a weak credit score, and hold a credit builder card, due to APRs that are often 30% or more.

Paying the full balance each month avoids interest on purchases. Understanding why it matters to only charge a credit builder card what can be repaid in full by the due date can help you manage the balance to your advantage. Here's a look at the potential costs of carrying a balance on a credit builder card.

ClearScore is a credit broker, not a lender.

Interest Payments

Since interest rates are higher on credit builder cards, carrying a balance means paying more in interest. Among ClearScore users approved for a credit card in early 2026, the median APR was 39.9% for scores below 400, compared with 26.9% for scores of 800 or more. The Bank of England's average quoted credit card interest rate was 24.71% in August 2026. This can have a significant effect on personal finances, especially for anyone working to improve their financial situation.

Many other factors affect the rate you're offered, and individual results vary.

Paying the full balance by each due date avoids interest charges entirely. The table below shows £1,000 of purchases, with no further spending, repaid by the minimum payment only, or by the minimum plus £20 a month. It assumes a minimum of the interest plus 1% of the balance, or £5 if that's higher. Minimum payment rules vary between cards. Our calculation.

Paying an extra £20 a month above the minimum payment clears the £1,000 in about 3 years 4 months at any of these rates.

Credit Score

Carrying a balance from month to month on a credit card, especially if you are near the limit and on a high-interest card, can affect a credit rating. Persistently carrying debt can be seen by lenders as an indication of difficulty managing existing borrowing, which can make it harder to access credit in future, or at a favourable interest rate.

Credit reference agencies collect information about your credit history and use it to produce credit reports and scores. Scores can differ between agencies, and lenders use their own scoring systems and criteria, so the score you see is not necessarily the score a lender uses.

Moving a balance to a balance transfer card

If a balance builds up on a credit builder card, moving it to a 0% balance transfer card can seem like an obvious next step. This can be more difficult than it sounds: those with a weaker credit score may find it harder to qualify for a 0% balance transfer card, though some options may still be accessible. Terms vary between cards.

A weaker credit history represents a higher potential risk to a lender, which is generally why a 0% balance transfer deal isn't guaranteed to be available.

Eligibility and acceptance are decided by each lender and depend on its own criteria and checks. Checking your eligibility does not guarantee that you'll be accepted.

What to Do

For some people, using a credit card carefully and repaying on time may help build credit history, but outcomes vary and eligibility is lender-dependent.

Credit cards for bad credit are designed for people with poor or limited credit history. They may have different eligibility criteria from standard cards, and typically have higher interest rates and lower credit limits.

Carrying a balance from month to month on a credit builder card can be costly, as the table above shows. If you find yourself struggling to pay back outstanding debt, free debt advice is available from organisations including National Debtline, Citizens Advice and StepChange.