Key figures — as of 2026-09-18: On a reference €150,000/30-year loan with a 1% spread, September's 12-month Euribor revision lifts the monthly payment to €712.15, up €70.48 on September 2025 — the steepest of the three revision tiers — while 6-month contracts rise €47.42 and 3-month contracts rise €23.82; August 2026's monthly Euribor averages were 2.513% (3-month), 2.713% (6-month) and 2.954% (12-month); by 8 September the 12-month rate itself had climbed to 3.177%, a fresh two-year-plus high; Banco de Portugal data (June 2026) show 6-month Euribor indexes 39.9% of variable-rate housing stock versus 31.3% for 12-month contracts.
The number that matters this month
Homeowners whose mortgage came up for its annual revision this September got an unwelcome letter from their bank. Based on a scenario with financing of €150,000 over 30 years and a spread of 1%, contracts with 12-month Euribor revised in September now pay €712.15, up €70.48 compared with September 2025. That's the biggest jump of the three revision windows DECO PROteste tracked this month — bigger than the six-month reset in March and the three-month reset in June.
Six-month Euribor contracts rose €47.42 to €691.53 compared with March, while three-month contracts rose €23.82 to €674.66 compared with June. The driver behind all three is the same: in August, the monthly average Euribor stood at 2.513% for three months, 2.713% for six months and 2.954% for 12 months, and the average used to revise a variable-rate loan is generally the one from the month before the contract's revision date.
Why 12-month contracts got hit hardest
It isn't the most common index in Portugal — that's still six-month Euribor. Bank of Portugal data show six-month Euribor mortgages account for 39.9% of the stock of variable-rate loans for permanent homes, with 12-month contracts at 31.3% and three-month contracts at 24.38%. But because 12-month contracts only reprice once a year, they absorbed twelve full months of the rate's climb in one hit rather than spreading it across shorter, more frequent adjustments — which is why the September jump landed hardest on that group.
The underlying rate hasn't stopped climbing either. The 12-month Euribor rose again in early September to 3.177%, a new high since August 2024. Markets aren't betting on relief soon: futures curves as of 17 September implied the 12-month rate reaching 3.589% by December 2026.
GrowIN's take: the annual bill, not just the monthly one
Run the DECO PROteste numbers forward and the household-budget impact becomes clearer. An extra €70.48 a month on a 12-month reset works out to roughly €845.76 in additional payments over the coming year for a household on that reference loan — and against the previous instalment of about €641.67, that's an increase of close to 11%, not a rounding error. For a foreign family who financed a Portuguese home with a 12-month variable mortgage and budgeted in their home currency, an 11% jump in euro terms compounds with exchange-rate swings most banks don't factor into affordability checks at origination.
"An 11% jump on a single annual reset is exactly the kind of shock that catches foreign buyers out, because Portuguese variable mortgages don't come with the payment caps some home countries build in," says GrowIN Portugal Editorial.
The extra squeeze on foreign residents
Non-resident and newly arrived buyers already start from a weaker position. Non-residents are typically offered a lower loan-to-value ratio and a higher spread percentage than residents — meaning the same Euribor rise translates into a larger euro increase on their instalment than on a comparable resident's loan. Anyone who financed a purchase through our relocation process in the last two or three years, when spreads and LTVs for non-residents were already tighter, is likely feeling this reset more acutely than the DECO PROteste reference case suggests.
What to watch next
Three-month contracts reprice again in September; six-month contracts next reset in around March 2027; 12-month contracts won't move again until September 2027 — so this rate is now locked in for a year regardless of what Euribor does next. Homeowners with upcoming revisions should ask their bank about switching to a fixed or mixed-rate period, and should check the European Central Bank's rate path before their next reset date. None of this is financial advice — a mortgage adviser or your bank can model the fixed-versus-variable trade-off against your specific loan balance and remaining term.
Euribor resets aren't going away, and this September's numbers are a reminder that variable-rate exposure cuts both ways — foreign homeowners who benefited when rates fell are now the same ones absorbing the climb back up.