POLSTR Replaces WIBOR: What Changes for Mortgage Borrowers in 2027
Poland's new POLSTR interest rate index will replace the long-used WIBOR starting January 1, 2027, for all new mortgage loans. Existing WIBOR mortgages remain unaffected until 2036, but borrowers should understand how the transition affects new rates.
The Transition: WIBOR to POLSTR
POLSTR (Polish Short Term Rate) is a new reference rate that will eventually replace WIBOR in variable-rate mortgages. From January 1, 2027, POLSTR will be the only index used in new mortgage contracts. Until the end of 2026, banks may still issue loans using WIBOR in parallel with POLSTR. If you already have a WIBOR-based mortgage, you don't need to do anything—WIBOR will continue to work in existing contracts until the end of 2036.
Why the Change?
POLSTR is based on real, overnight transactions between banks rather than declarations, a different mechanism from WIBOR, though the way interest is built (base rate plus bank margin) remains unchanged. WIRON (Warsaw Interest Rate Overnight) was introduced in new loans from 2025 to replace WIBOR, based on actual overnight transactions. This shift aims to create a more transparent, market-driven rate.
Practical Impact for Borrowers
WIBOR 3M, which sets the variable portion of most mortgages, has fallen from a peak of 7.5% in early 2023 to around 4.5–5.0% by mid-2026. Variable rates tied to WIBOR 3M or WIRON recalculate whenever the National Bank of Poland reference rate moves. For those planning a new mortgage after December 31, 2026, your rate will be quoted as POLSTR + bank margin instead of WIBOR + margin.
The lower WIBOR rates have meaningfully reduced monthly payments compared to mortgages issued two to three years ago. When comparing POLSTR-based offers in 2027, focus on the total rate (index plus margin), not just the index itself—bank margins vary and can offset any index advantage.
For Expats and Foreign Residents
If you are considering a mortgage in Poland or already hold a WIBOR loan, now is a good time to review your options. Banks categorize foreign borrowers not by nationality but by income type and residency stability. The simplest path is a foreigner with a permanent residence card or long-term EU resident status, working under an indefinite employment contract. Speak with your bank about whether a fixed-rate mortgage (locked for 5–10 years) or a variable rate suits your financial situation. Most importantly, if you already have a WIBOR mortgage, you are not obligated to switch—the 2026 transition concerns only new loans signed from January 2027 onward.
Sources
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