PKO Bank Polski Switches from WIBOR to POLSTR — What Mortgage Borrowers Need to Know

From 3 September 2026 PKO Bank Polski stopped applying the WIBOR benchmark to new mortgage loans and switched to POLSTR (Polish Short-Term Rate). This is not an isolated decision — it is part of a wider transition of the entire Polish banking sector to new reference rates, mirroring the global LIBOR reform. Below we explain what this means for new borrowers and for existing WIBOR-linked mortgage holders.

Key fact: POLSTR is based on actual money-market transactions rather than bank estimates, making it more transparent and harder to manipulate than WIBOR.

What is WIBOR and why is it being replaced?

WIBOR (Warsaw Interbank Offered Rate) is the rate at which banks declared their willingness to lend to each other on the interbank market. It attracted criticism for being based on estimates rather than actual transactions — potentially opening the door to manipulation, similar to the LIBOR scandal that shook global markets. Poland’s Financial Administration (PASF) developed POLSTR as a transaction-based replacement.

What is POLSTR and how is it calculated?

POLSTR is calculated from real overnight lending transactions on the Polish money market. It is published daily by the National Bank of Poland (NBP) and is derived from data submitted by market participants. Because it is transaction-based rather than estimate-based, it is more transparent. For mortgage purposes a compounded average version (POLSTR 1M or 3M) is used rather than the overnight rate directly.

How will this affect mortgage repayments?

The difference between POLSTR and WIBOR depends on the current shape of the yield curve. In stable conditions both rates tend to move closely together. However, when rate cuts are expected POLSTR (as a short-term rate) responds faster than WIBOR 3M or 6M — which can benefit borrowers if the Monetary Policy Council cuts rates. Conversely, during rate hikes POLSTR may rise more quickly.

What does this mean for existing WIBOR borrowers?

If you have a WIBOR-linked mortgage taken before 3 September 2026, your existing terms remain unchanged until your bank contacts you about conversion. Each bank sets its own conversion timeline for existing loans, which requires an addendum to the contract. There is no obligation to convert immediately — you have time to review the proposed terms.

What to check when converting your loan

When reviewing an addendum that converts WIBOR to POLSTR check: the margin after conversion (it should remain the same), the compounding method for POLSTR (1M, 3M or another variant) and the effective date of the new rate. If the bank proposes a margin change during conversion you have the right to negotiate or refuse. If in doubt, consult a lawyer or independent financial adviser.