PKO BP First to Introduce POLSTR for Mortgages, but Cheaper Loans Are Not Guaranteed

PKO Bank Polski will be the first major Polish bank to bring POLSTR into new variable-rate mortgages, but borrowers should not assume the change will automatically lower their monthly costs.

PKO BP and PKO Bank Hipoteczny said they would begin offering the loans on Sept. 3, 2026. The move follows a reform timetable under which banks should stop signing new contracts based on WIBOR from the beginning of 2027. POLSTR is therefore expected to appear across the banking sector’s new variable-rate mortgage products by the end of this year.

At first glance, the new benchmark looks favorable to customers. On Aug. 31, the three-month WIBOR rate stood at 3.8%, while POLSTR 1M Stopa Składana, the rate PKO BP plans to use, stood at 3.55%. But the benchmark is only one part of a mortgage’s interest rate. The final rate combines the reference rate with the bank’s margin. If a bank sets a higher margin for a POLSTR-based loan than it previously charged on a WIBOR-based mortgage, the advantage of the lower benchmark could disappear entirely.

That means borrowers will have to wait for banks to publish their complete offers before deciding whether the new mortgages are genuinely cheaper. PKO BP has not yet disclosed all of those terms.

POLSTR is administered by GPW Benchmark and is based on actual overnight transactions in the financial market. Those transactions are used to calculate compounded rates for longer periods, including one, three and six months. The model forms part of a broader reform intended to make reference rates more transparent and more closely tied to real market activity.

Other banks are expected to follow PKO BP. Some have already said they plan to launch POLSTR-based variable-rate mortgage products in the fourth quarter of this year. The change does not affect fixed-rate or temporarily fixed-rate loans, and it does not automatically alter mortgages that borrowers are already repaying. Existing WIBOR-linked loans will continue under their current terms.