Poland's Biggest Mortgage Rate Reform in Years
On 29 May 2026, GPW Benchmark — the Polish company responsible for calculating reference rates — published an official timetable for replacing the WIBOR benchmark with the new POLSTR (Polish Short-Term Rate). From early 2027, Polish banks will stop issuing new variable-rate mortgages based on WIBOR. All new floating-rate agreements will be tied exclusively to POLSTR. If you have a mortgage in Poland, or plan to take one out, this change affects you directly.
WIBOR vs POLSTR: What's the Difference?
WIBOR — a declaration-based rate
WIBOR (Warsaw Interbank Offered Rate) was the rate at which banks stated they were willing to lend to each other. The key word is stated — it was calculated from survey submissions, not actual market transactions. Following the global LIBOR scandal, European regulators pushed for a shift to transaction-based benchmarks.
POLSTR — a transaction-based rate
POLSTR is calculated from actual overnight deposit transactions conducted between financial institutions on the Polish wholesale money market. This is the same approach used across Europe — ESTR in the eurozone, SONIA in the UK. It is more transparent and reflects the real cost of money in the market.
Will My Monthly Payment Change?
The adjustment spread
POLSTR is typically 0.2–0.4 percentage points lower than WIBOR at the same NBP rates — which sounds like good news for borrowers. However, when switching existing contracts, banks will apply an adjustment spread — a fixed add-on that compensates for the structural difference between the two rates. The result: your monthly payment should stay roughly the same after the switchover.
More frequent rate updates
One practical change for new mortgages: instead of WIBOR 3M (rate updated every three months), new contracts will predominantly use POLSTR 1M — updated monthly. This means you'll see the benefit of NBP rate cuts faster, but equally, any hikes will feed through to your payment more quickly.
Timeline — Key Dates
- June 2025 — GPW Benchmark begins publishing POLSTR.
- September 2025 — POLSTR gains official benchmark status.
- December 2025 — first bank products linked to POLSTR appear.
- Q2 2026 — banks begin rolling out POLSTR-based mortgages for retail clients.
- End of 2026 — banks stop issuing new WIBOR-linked loans.
- 2027 — all new variable-rate mortgages exclusively on POLSTR.
- 2037 — existing WIBOR contracts converted to POLSTR.
I Already Have a WIBOR Mortgage — Do I Need to Act?
No. If you are currently repaying a mortgage linked to WIBOR 3M or 6M, your contract remains unchanged until early 2037. The conversion will happen automatically, with banks legally obliged to maintain the economic balance of your agreement. No action, calls or signatures are required on your part.
The one scenario where you should pay attention: refinancing. If you remortgage with a different bank, your new contract will already be on POLSTR. That's a good moment to shop around — a margin difference of just 0.3 percentage points on a PLN 400,000 balance saves over PLN 1,200 per year. Compare current offers at BankSorter.com.
Current Market Context: NBP Rates in June 2026
In June 2026, the Monetary Policy Council (RPP) held the NBP reference rate steady at 3.75% — the lowest level in four years, following a cumulative 2 percentage-point cut over the past twelve months. WIBOR 3M currently sits at around 5.5%. Most analysts expect no further cuts before end-2026; the next possible reduction is pencilled in for early 2027 at the earliest.
What Should You Do Now?
If you are taking out a new mortgage in 2026
Ask your bank whether they already offer POLSTR-based mortgages — some are rolling them out in Q2 2026. Compare a POLSTR floating-rate offer against a fixed-rate product (5 or 7 years). If you expect NBP cuts in 2027, the floating rate may prove cheaper. If you value payment certainty, fixed is safer.
If you already have a WIBOR mortgage
Nothing urgent — you have until 2037. But it is worth checking annually whether refinancing to a bank with a lower margin makes financial sense. Use our mortgage comparison tool and savings accounts comparison to see whether overpaying your loan beats waiting for rate cuts.
Summary
The WIBOR-to-POLSTR reform is a major institutional shift but, in practice, an orderly evolution for most borrowers. The adjustment spread mechanism ensures the transition is financially neutral. For new borrowers, POLSTR brings greater transparency. For existing ones — stability until 2037 and an automatic switchover. Ready to find the best mortgage offer in today's market? Compare all Polish bank offers on BankSorter.com.