Reading your mortgage statement — why the payment keeps moving

Capital, interest, Euribor, spread, two insurances — what each line of the prestação actually is, and which numbers deserve your attention.

By António Avelar · Updated 19 August 2026 · 3 min read

For most people the mortgage is the largest number that leaves the account every month, and also the one they understand least. The bank sends a statement, the amount changes twice a year, and the honest reaction is to check that it was paid and move on.

That works until the payment jumps and you can’t say why, or until you want to renegotiate and don’t know which number to argue about. Reading the statement takes ten minutes once you know what each line is.

The prestação is two numbers pretending to be one

Every monthly payment splits into capital — the part that actually reduces your debt — and interest, the part that is the bank’s price for the loan.

The split is not fixed, and early on it is not flattering. In the first years of a thirty-year loan, well over half of each payment can be interest. The proportion shifts toward capital slowly, month by month, following an amortisation schedule the bank computed on day one. This is why a mortgage feels like it barely moves at the start: it does barely move.

The statement shows both numbers. The one that measures progress is the remaining capital — capital em dívida. Watch that one, not the monthly amount.

Where the interest rate comes from

Unless you fixed the rate, your interest is the sum of two parts: an index and a spread.

The index is Euribor — at three, six or twelve months, whichever your contract names. It moves with the market and your bank has no say in it. Which term you have determines how often your payment changes: a six-month Euribor means the rate is recalculated every six months, on a revision date the contract fixes.

The spread is the bank’s margin, agreed at signing and printed in the contract. It does not move on its own — but it is the one part of the rate you can negotiate, and the number to compare when another bank offers to take the loan over.

When the payment jumps, it is almost always the index that moved at a revision date. The statement names the current rate (TAN) and the next revision; those two facts explain nearly every surprise.

The two insurances riding along

A Portuguese mortgage carries life insurance and multi-risk home insurance, and both usually leave the same account — sometimes inside the prestação, sometimes as separate debits that look cryptic on the statement.

The detail worth knowing: banks commonly grant a spread discount for holding their insurance, and the insurance is often priced well above what an outside insurer charges for the same cover. The discount and the overpricing can cancel out — or not. Once a year, price both separately and do the arithmetic. The fixed-costs audit treats insurance in general; the mortgage pair is the largest case of it.

The three numbers worth writing down

You do not need to study the statement monthly. You need three numbers from it, checked at each revision:

1. Remaining capital — the actual size of the debt, and the base for any early-repayment maths.
2. Current rate and next revision date — so a payment change is an expected event, not a shock.
3. The spread — your negotiating position, fixed in the contract but not in stone.

Treat it as a fixed cost, because it is one

The prestação belongs in the same list as telecoms and insurance: a fixed cost that leaves on its own and rewards an annual look. The difference is scale — a 0.2-point spread improvement on €150,000 is around €25 a month, which makes it the single most valuable phone call on the list.

The statement is the bank telling you, precisely, what the loan costs. The only mistake is not reading it.