Track principal · Map payment changes
Interest-only payments and negative amortization
A low initial payment can leave principal unchanged—or even make the mortgage balance grow.
The short answer
Interest-only payments cover interest but do not reduce principal. Negative amortization means the payment does not cover all interest, so unpaid interest is added to principal and the balance increases.
01 · Baseline
Amortizing payments reduce principal over time
In a typical fully amortizing mortgage, each principal-and-interest payment covers accrued interest and applies something to principal. The balance falls over time and reaches zero at the end of the term if payments are made as scheduled.
02 · Principal stays flat
An interest-only payment does not pay down the amount borrowed
During an interest-only period, the scheduled payment covers interest but requires no principal reduction. Making every required payment can therefore leave the original principal balance unchanged until the interest-only period ends.
03 · Principal grows
Negative amortization adds unpaid interest to the balance
If a permitted minimum payment is less than the interest that accrued, the unpaid interest can be added to principal. The borrower then owes more after paying, and future interest may be calculated on the larger balance.
With interest-only, principal generally stays level during the specified period. With negative amortization, principal grows because the payment did not cover all accrued interest.
04 · Payment transition
The payment can rise even if the interest rate does not
When the initial period ends, the remaining—or increased—balance may need to be repaid over fewer years. The required payment can rise substantially when principal repayment begins. If the rate is also adjustable, a rate change can add another source of payment risk.
CFPB warns against assuming a home can be sold or the loan refinanced before that increase. Property value, finances, rates, and credit availability may change.
05 · Disclosure trail
Read the product description and every projected payment phase
A Loan Estimate identifies negative amortization in the product description and shows expected payment changes. Review Loan Terms, Projected Payments, and any adjustable-rate tables, then confirm the final Closing Disclosure and Note use the same structure.
06 · Whole-loan review
Compare balance paths, not only first payments
Ask for the balance after each payment phase and the first fully amortizing payment. Compare those figures with a loan that begins principal repayment immediately. Include the rate, APR, fees, term, balloon features, caps, and total costs over the same period.
- Whether each payment covers interest and any principal
- Interest-only or minimum-payment period and exact end date
- Balance at the end of each payment phase
- First fully amortizing payment after the payment change
- Rate adjustments, caps, index, margin, and payment limits
- Loan term, balloon amount, fees, APR, and total costs
07 · Statement audit
Track principal, interest, and ending balance separately
Do not use the fact that a payment was accepted as proof that the balance fell. Compare consecutive statements and ask the servicer to explain any increase or any posting that differs from the contract.
- Loan Estimate product description and Loan Terms
- Projected Payments and adjustable-rate tables
- Closing Disclosure and promissory Note
- Amortization schedule for every payment phase
- Statements showing interest, principal, and ending balance
- Written explanation of minimum-payment and recast triggers
08 · Official guidance