How a card balance actually charges you
The technique
A card's rate is monthly, and the minimum due is built to keep it running
Cards quote interest as a monthly rate, commonly around 3.5 percent, and the mind reads it as if it were annual. It is not. It is about 42 percent a year before GST, it accrues daily on the unpaid balance from each transaction date once you carry anything past the due date, and the minimum due is set just high enough to keep the account current and just low enough that the principal barely moves.
Take ₹1,50,000 outstanding at an illustrative 3.5 percent a month. One month's interest is ₹5,250. GST at 18 percent applies to the interest, which adds ₹945, so carrying the balance for a month costs ₹6,195, or roughly ₹207 a day. Nothing on that statement reduces the debt; it is the price of standing still.
Now the minimum-due schedule. Issuer formulas vary, so this is a model: assume the minimum due each month is 5 percent of the balance plus that month's interest plus GST on the interest, and that you pay exactly that and never spend on the card again.
| Month | You pay | Of which interest + GST | Balance after |
|---|---|---|---|
| 1 | ₹13,695 | ₹6,195 | ₹1,42,500 |
| 3 | ₹12,360 | ₹5,591 | ₹1,28,606 |
| 12 | ₹7,790 | ₹3,524 | ₹81,054 |
| 24 | ₹4,209 | ₹1,904 | ₹43,798 |
| 60 | ₹664 | ₹300 | ₹6,910 |
| 143 | ₹9 | ₹4 | ₹98 |
- Paying the minimum on ₹1.5 lakh takes about 143 months, nearly twelve years, and costs ₹1,23,819 in interest and GST on the way: total outgo ₹2,73,721 to clear ₹1,50,000
- The first year alone charges ₹56,949 in interest and GST while clearing ₹68,946 of principal. Almost half of what you pay in year one buys you nothing
- The schedule assumes you stop using the card. A card carrying a balance has no interest-free period on new spends, so every purchase joins the balance at the full rate from its transaction date






