Key takeaway
A 0% period ends in one of two ways: the remaining balance quietly starts accruing at the go-to rate (waived interest), or a year's worth of background interest detonates at once on the original purchase amount (deferred interest — about $2,069 on a $6,000 purchase at 29.99%). Know which type you have, divide the balance by the promo months, automate that payment, and run the go-to-rate math on any remainder before the deadline arrives.
The two kinds of 0%
Waived interest (true 0%): interest is simply not charged during the promo. When it ends, whatever balance remains starts accruing at the regular "go-to" rate. Most general-purpose credit cards (Visa, Mastercard, Amex, Discover) work this way.
Deferred interest: interest is accruing in the background the entire time at the full rate — it's just not billed yet. If you pay the balance down to exactly $0 before the promo ends, the accrued interest is forgiven. If even $1 remains, all of it comes due at once, calculated on the original purchase amount — not the remaining balance. Store cards and medical financing ("no interest for 12 months!") overwhelmingly use this structure.
This is the single most important distinction in 0% financing. Everything below follows from it.
The deferred-interest trap, worked out
A $6,000 furniture purchase on a store card: 0% for 12 months, deferred interest at 29.99% APR.
You pay diligently — $5,500 over the year, leaving just $500 unpaid in month 12. Surely the penalty is small?
- Background interest accrued: about $2,069 for the year ($6,000 at 29.99%, compounded monthly — daily compounding would be a touch higher).
- Because $500 remains, the full $2,069 is billed retroactively.
- Your $500 remainder becomes a $2,569 balance overnight.
You paid off 92% of the purchase and still got hit with interest on 100% of it. That asymmetry — penalty calculated on the original amount, not what's left — is what makes deferred interest so punishing. The disclosure is usually there ("if the balance is not paid in full, interest will be charged from the purchase date"), but it's rarely understood until the bill arrives.
The defense is binary and unforgiving: with deferred-interest financing, the balance must hit exactly zero before the deadline. Divide the purchase by the promo months and automate it — $6,000 ÷ 12 = $500/month, not the card's minimum.
The waived-interest outcome (much kinder)
Same $6,000 purchase on a true 0% card, $5,500 paid, $500 remaining at month 12:
- No retroactive interest. The $500 simply starts accruing at the go-to rate — say 24.99%.
- That's about $10.41/month in interest going forward.
The difference between the two structures on the identical payment behavior: $2,069 vs. $0 retroactive. Always identify which type you're holding before you buy — it's in the Schumer box or the promo terms, usually under "deferred interest" or "interest will be imposed from the transaction date."
The go-to rate: doing the forward math
When any 0% promo ends (waived type) or you carry a transferred balance, the go-to rate takes over. Run it before the promo expires:
| Remaining balance | Go-to APR | Monthly interest |
|---|---|---|
| $2,000 | 24.99% | ~$41.65 |
| $4,000 | 24.99% | ~$83.30 |
| $4,000 | 29.99% | ~$99.97 |
A $4,000 remainder at 24.99% costs $83.30 a month in interest alone — which means a $150 minimum payment retires barely $67 of principal. If your post-promo plan was "minimums for a while," the go-to rate math usually kills it; the balance needs an aggressive payoff schedule starting the month the promo ends, not three months later.
The minimum-payment trap inside the promo
Many 0% offers set the minimum payment far below what's needed to clear the balance in time. A $6,000 balance on an 18-month 0% transfer with a $120 minimum: 18 × $120 = $2,160 paid, leaving $3,840 to detonate at the go-to rate. The minimum is designed around the issuer's risk, not your deadline. The number that matters is always balance ÷ promo months — $6,000 ÷ 18 = $334/month — set that as the autopay and ignore the minimum. For the full minimum-payment math, see the minimum-payment trap.
What to check before you sign
- Deferred or waived? Search the terms for "deferred interest." If present, treat the deadline as absolute.
- What is the go-to rate, and when exactly does it apply? Note whether it applies to the remaining balance only (waived) or retroactively (deferred).
- Does the promo cover purchases, transfers, or both — and do new purchases get the same terms? Mixed terms are common.
- What voids the promo? A single late payment can terminate 0% early on some cards.
Model your 0% exit before the deadline
Our free balance transfer analyzer compares staying put vs. transferring — total cost, the monthly payment that clears the balance in time, and whether the transfer fee pays for itself.
Related calculators
- Balance Transfer Analyzer — is a 0% transfer worth the fee on your numbers?
- Debt Payoff — avalanche vs. snowball payoff plans compared.
- The Minimum-Payment Trap — why minimums alone take decades.
Frequently asked questions
What is deferred interest?
Interest that accrues in the background at the full APR during a 0% promo but isn't billed — yet. Pay the balance to exactly $0 before the deadline and it's forgiven; leave even $1 and the entire accrued amount comes due at once, calculated on the original purchase amount. Store cards and medical financing most commonly use this structure.
What's the difference between deferred interest and a true 0% APR?
With waived (true 0%) interest, no interest accrues during the promo — when it ends, only the remaining balance starts accruing at the go-to rate. With deferred interest, a full period's interest has been silently accumulating and detonates retroactively if any balance remains. Check the terms for the words “deferred interest” before you buy.
How much can deferred interest add to my bill?
On a $6,000 purchase at 29.99% deferred for 12 months, about $2,069 — billed all at once on the original $6,000, even if you paid off 92% of it. Your $500 remainder becomes a $2,569 balance overnight. That asymmetry is what makes deferred interest so punishing.
What is the go-to rate?
The regular APR that applies when the promo ends — e.g., 24.99% on the remaining balance. At 24.99%, a $4,000 remainder costs about $83.30/month in interest alone, so minimum payments barely dent principal. Run the go-to-rate math on any expected remainder before the deadline, not after.
How do I guarantee I pay off a 0% balance before the deadline?
Divide the starting balance by the promo months and automate that payment — $6,000 ÷ 18 months = $334/month — and ignore the card's minimum, which is set far too low to clear the balance in time. With deferred-interest financing the balance must hit exactly zero, so build in a one-month buffer and confirm the payoff posted.
Last updated: September 28, 2026