The Minimum Payment Trap, in Numbers

$6,000 on a card at 24.99%, paid at the minimum and never used again, takes 254 months to clear. That is 21 years and 2 months, and $11,360.48 of interest against $6,000 borrowed. You will have repaid $17,360.48 and made every payment on time.

Nothing in that is a penalty or a trick clause. It is the minimum payment formula working exactly as designed, and the design is worth understanding, because once you see it the fix is obvious and costs nothing.

How is the minimum actually calculated?

Most US issuers use some version of the same formula: 1% of the balance, plus the interest and fees charged that month, with a floor of around $25. Your card agreement states yours under "minimum payment", and it is worth reading, because some issuers use 2% and a few use a flat percentage with no interest add-on.

Take the first month of a $6,000 balance at 24.99%.

68% of that payment is rent on money you have already spent. The CFPB's explanation of how a card company calculates interest covers the daily-balance mechanics behind that $124.95.

And here is the thing almost nobody notices: the formula is a percentage of the balance. So as the balance falls, the payment falls too.

Why does the payment shrink?

Both components shrink together. Less balance means less interest and a smaller 1%. The payment that was $184.95 in month one is $165.59 by month twelve and $102.22 by month sixty.

Read the third column down. Your payment gets easier every single month, which feels like progress and is the opposite of it. You are decelerating. After five years of faultless payments the balance is still $3,316.10, and you are now paying $102 a month against a debt that started at $6,000.

Notice the last row. By month 240 the percentage formula has fallen under the $25 floor, so the floor takes over and the debt finally starts clearing at a decent clip. That is why it ends at 254 months rather than never: the floor rescues you, seventeen years in.

This is the trap, and it is structural rather than malicious. A payment that falls with the balance is a payment that can never finish the job quickly, because the amount of work it does shrinks in proportion to the work remaining.

What does $50 more a month change?

More than anything else you could do with $50.

The first $50 buys back $7,048.36 and fourteen and a half years. The next $100 buys $2,276.44 more. The one after that buys $874.30. Each extra dollar is worth less than the one before it, which is exactly backwards from how people budget for this: the temptation is to wait until you can afford a serious payment, and the serious payment is worth proportionally less than the small one you could start tomorrow.

There is also a free version of this. Most of the damage comes from the payment shrinking, so fix your payment at today's minimum and never let it drop. It costs you nothing today, it is a single standing instruction, and it converts a 254-month schedule into something closer to the second row of that table.

Read the box on your statement

Every US card statement carries a minimum payment warning, required since the CARD Act. It is a small box, usually on the first page, and it is the most useful thing your issuer sends you.

It tells you two numbers. First, how long the balance takes and what it costs if you pay only the minimum. Second, the payment that would clear it in three years, and what that costs.

On this card, that second figure is $238.53 a month, clearing the balance in 36 months for $2,586.98 of interest. Set against the minimum-only column, the box is telling you that $53.58 a month more than the first minimum saves $8,773.50.

Two things about it are worth knowing. The three-year figure assumes you stop using the card, so if you keep spending the box is describing a balance you do not have. And the minimum-only column assumes the shrinking minimum, which is why the number is so much larger than people expect when they first read it.

When the balance goes up while you are paying

The most demoralising version of this, and it has a simple cause.

Your minimum retires $60 of principal in month one. If you spend more than $60 on the card that month, the balance rises. You made the payment, the statement shows a higher number, and it reads as the card cheating.

It is not. It is $60 of repayment against, say, $180 of new spending. Any payoff plan on an active card has to start by stopping the spending, and that is harder than the arithmetic, because the card is usually attached to the direct debits and the shopping accounts that make up ordinary life.

There is also a slower version of the same problem, and it is the one that catches households who are careful rather than careless. If the card is quietly funding the expenses that were never in the budget, the annual insurance instalment, the tyres, the dentist, then the balance refills every year at roughly the rate you pay it down. The spending is not impulsive and the budget is not being broken. The expenses were simply never in it, which is what sinking funds explained is about, and no payment schedule survives that.

When this does not apply

If your card is at 0% on a promotional rate. The minimum is still shrinking, but nothing is accruing, so the trap is different. The risk is arriving at the end of the promotional window with a balance that then reprices, and the fix is to divide the balance by the months remaining and pay that, not the minimum. See balance transfers, and what they cost when they go wrong.

If you are genuinely unable to pay more than the minimum right now. Then pay the minimum, on time, every month, and do not let this article make you feel worse. On-time payment is 35% of a credit score and it protects everything you will want later. Meanwhile, the highest-value hour available to you is a call asking for a lower rate, which costs nothing and needs no extra money.

If your issuer uses a different formula. Some use 2% of the balance with no interest add-on, which is a larger payment early and a much shorter schedule. A few use a flat dollar minimum. Read your agreement rather than assuming the 1%-plus-interest version above, because the answer changes by years.

If the balance carries fees rather than purchases. Late fees and over-limit charges are added before the minimum is calculated, so the payment rises while the principal does not fall. The priority there is stopping the fees, and the CFPB's page on what to do about a fee is the place to start, because most of them are negotiable.

Next steps

1. Open your latest statement and find the minimum payment box. Write down both numbers it gives you.
2. Set a standing payment at today's minimum, so it can never shrink. This is free and it is most of the benefit.
3. Add whatever you can on top, and do not wait for it to be a respectable figure. The first $50 is worth more than the second $100.
4. Stop using the card while you do this, or the principal cannot fall.
5. If you carry more than one balance, decide the order before you start: avalanche or snowball, and what each one costs.