Loan principal
Principal is the money actually borrowed and still owed. Interest is the charge for having borrowed it. Every mortgage payment divides between the two, and understanding the split explains most of what people find confusing about mortgages.
The split, and why it moves#
Interest is calculated on the outstanding balance. At the start of a loan that balance is at its highest, so the interest portion of the payment is at its highest and the principal portion at its lowest.
As principal comes down, the interest charge on it comes down too — and since the total payment stays the same on a fixed-rate loan, the difference goes to principal. The shift compounds slowly at first and then quickly.
On a thirty-year mortgage the point where more of the payment goes to principal than to interest arrives well past the halfway mark in time. That is not a trick. It is the arithmetic of charging interest on a declining balance.
What principal is not#
It is not the payoff figure. A payoff quote adds interest accrued to the payoff date, plus any fees, escrow deficiency, or amounts the servicer advanced for taxes or insurance.
It is also not the whole monthly payment. The familiar acronym PITI — principal, interest, taxes, insurance — exists because only the first two parts are the loan. The other two are money passing through.
Why it decides everything downstream#
Equity is market value minus what is owed, and what is owed starts with principal. Whether a property can be refinanced, sold at a profit, or redeemed after a foreclosure sale all trace back to this number.
It is also the number that determines whether a sale covers the debt. Where it does not, the shortfall becomes a deficiency — and whether that shortfall is collectable is a separate question governed by state law.
Where the balance appears, and why the figures differ#
Three documents show a principal balance and none of them agree.
The monthly statement shows principal as of the last payment posted. It is the cleanest number and it is already out of date.
The payoff quote adds interest accrued to a stated payoff date, plus fees and any escrow deficiency. It is larger, and it expires — a quote good through the fifteenth is short if the money arrives on the twentieth.
The credit report balance lags both, often by a full billing cycle, and is the wrong figure to use for any decision.
For anything consequential — a sale, a refinance, a redemption — use a written payoff quote and watch its expiry date.