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A revolving card is a credit card that does not charge you the whole purchase at the end of the month: it lets you defer it and charges interest on what is left. With a 3,000-euro balance, a 24% APR — an ordinary rate for this product — and a minimum payment of 60 euros, the arithmetic runs like this:
1. A 24% APR works out at 1.81% a month: on 3,000 euros, 54.26 euros in the first month. 2. Of your 60 euros, 54.26 pay interest and 5.74 come off the debt. Next month you owe 2,994.26. 3. At that rate it takes 131 months — ten years and eleven months — to reach zero, and you will have paid back 7,860 euros for 3,000. 4. If you use the card again, the minimum payment is recalculated on the new balance: some statements sit at the same figure for years. 5. With 200 euros a month, the same debt is gone in 18 months and costs 530 euros of interest instead of 4,860.
The statement shows the payment amount, not the split between interest and capital. Ask your bank for the amortisation table and look for the capital-repaid column: if it is under 20% of the payment, the debt is barely moving.
Spain's Supreme Court ruled a revolving card at 26.82% APR usurious in March 2020, taking as its benchmark the average rate the Bank of Spain publishes for this same product.