A 0% offer ends on a date. Know which kind you have before it does.

What a 0% period is

A 0% introductory APR means the card charges no interest on the covered balance for a set time. Offers can cover purchases, balance transfers, or both, and the 2 periods are not always the same length.

The issuer must tell you how long the rate lasts and what rate follows. The CFPB states that an introductory rate must last at least 6 months unless you are more than 60 days late.

What happens the day it ends

On a true 0% offer, nothing is charged for the months already passed. From that day on, the remaining balance collects interest at the card’s regular rate, and many card companies calculate that interest daily.

The CFPB lists the end of a temporary rate as 1 of the allowed reasons a card company can raise the rate on a balance you already have. It is not a surprise change. It is the deal you accepted.

Deferred interest is different

Store cards and medical cards often use a different offer: no interest if paid in full within a set number of months. The CFPB explains that this is a deferred interest plan.

If you pay the whole purchase off in time, you pay no interest. If any amount is left at the deadline, or you are more than 60 days late on a minimum payment, you can be charged interest on the balance you owed in each month, all the way back to the purchase date.

Why minimum payments are not enough

The CFPB warns that minimum payments probably will not pay off the balance by the end of a deferred interest period. The same is true of most 0% offers. The minimum is set to keep the account current, not to finish on time.

Divide what you owe by the months left. That is your real payment. If you cannot afford it, you now know that today instead of in the last month.

How payments are split

If the same card holds a promotional balance and a regular-rate balance, the amount you pay above the minimum generally goes to the higher-rate balance first. That can leave the promotional balance untouched for months.

The CFPB notes 1 exception for deferred interest: in the last 2 billing cycles before the deadline, the amount above the minimum goes to the deferred interest balance. Do not wait for those 2 cycles. Keep other spending off a card that carries a deferred interest purchase.

Protect the offer

Pay on time, every time. The CFPB says a card payment generally cannot be treated as late if the company receives it by 5 p.m. on the due date. Automatic payments remove the risk.

A single late payment can still bring a late fee. Being more than 60 days late can cost you the promotional rate itself.

If you will not finish in time

You have options, and they work better early. Raise the monthly payment. Move the remaining balance to another low-rate card, counting the transfer fee. Ask the issuer what it can offer. Or accept that a known amount will collect interest and pay it down fast.

On a deferred interest plan, paying the last dollar before the deadline matters more than anything else. Borrowing a small amount elsewhere to clear it can cost far less than the interest that would be added back.

After the offer

Once the balance is gone, the card is just a card. Decide whether its rewards and fee earn it a place. If you carry a balance again later, the CFPB notes that most cards charge interest on new purchases from the day you make them until you return to paying in full.