Balance transfer cards: when they help and when they hurt

The basic idea

You move an existing balance to a new card with a 0% promotional period, pay a one-off transfer fee, and every payment during the promo goes to principal instead of interest.

The maths in three lines

1. Fee = balance x fee percentage. Add it to the balance. 2. Required monthly payment = new balance / promo months. 3. If you cannot afford that payment, the transfer only delays the problem.

Where it goes wrong

Spending on the new card. New purchases often sit at the standard rate and can be paid off last. Missing the deadline. When the promo ends, the remaining balance jumps to the full rate. Missing a payment. Some deals end the promotional rate entirely. Serial transferring. Each hop adds a fee and a hard search.

Is it worth it?

Compare the fee against the interest you would otherwise pay over the same period. If the interest saved comfortably beats the fee and you can clear the balance inside the promo, it is a good deal. Model both scenarios in the debt payoff calculator.

Do not forget utilisation

Opening a new card changes your total available credit and your utilisation ratio. Usually that helps, as long as you do not treat the freed-up limit as spending money. See credit utilisation explained.

Set the payment before you transfer

Work out the required monthly payment and set the standing order the same day the transfer completes. That single step is the difference between a smart move and an expensive one.