WIBOR to POLSTR: what the benchmark switch means for your mortgage in Poland

WIBOR is on the way out: the timeline that matters

Most variable-rate mortgages in Poland are priced as WIBOR plus a fixed bank margin. WIBOR (Warsaw Interbank Offered Rate) is a benchmark that reflects where banks expect short-term interest rates to be over the next 1, 3 or 6 months. Its level tracks the decisions of the RPP, Poland's Monetary Policy Council, which sets the official rates of the National Bank of Poland (NBP). At its meeting on 7-8 July 2026 the RPP kept the reference rate at 3.75%, the fourth month in a row without a change.

On 30 June 2026 the steering committee of the National Working Group for benchmark reform (KS NGR) approved an updated roadmap for retiring WIBOR. Two dates matter for borrowers. From the beginning of 2027, WIBOR and WIBID may no longer be used in new contracts and financial instruments. And 31 December 2036 is planned as the last day the 1M, 3M and 6M WIBOR tenors are published, which means existing contracts can keep running on WIBOR until then.

This is a major softening compared with the previous version of the roadmap from March 2025, which assumed WIBOR publication would end as early as the start of 2028, with existing contracts converted by government regulation. The scale explains the caution: at the end of 2025 around 3.9 million contracts in Poland were based on WIBOR, including roughly 1.7 million mortgages and 1.3 million consumer loans.

POLSTR: how the new benchmark works and where it stands today

POLSTR (Polish Short Term Rate) is calculated by GPW Benchmark, the same administrator that publishes WIBOR, but from a fundamentally different input: actual overnight deposit transactions between financial institutions, not declared expectations. Publication started on 2 June 2025, and the index comes out every business day at 12:55.

The mechanics differ in a way you would feel in your installment. WIBOR looks forward: the 3M tenor prices in what the market expects over the next three months. POLSTR Compounded looks backward: it compounds the overnight rates actually recorded over the past period. A WIBOR 3M loan resets its rate every three months, while a loan based on POLSTR Compounded updates monthly. When rates fall, POLSTR passes the cuts to your installment faster; when they rise, it passes the hikes faster too.

Two readings matter. The daily POLSTR index (3.383% on 5 August 2026) swings from day to day, so for loan comparisons the compounded term rates are the right yardstick. On that basis POLSTR 3M Compounded, at about 3.58%, sits roughly 0.25 percentage points below WIBOR 3M at 3.83%. With the same margin, a loan priced on POLSTR would be cheaper today.

The draft law: a mandatory offer, a voluntary switch

The mechanism for moving existing borrowers is set out in draft law UC132, prepared by the Ministry of Finance and Economy. As of the turn of June and July 2026 the draft was in public consultations, so everything below is a proposal, not binding law. Under the draft, within 9 months of the rules taking effect every bank would have to send each client with a WIBOR-based contract a conversion offer with two options: a fixed interest rate or a variable rate based on POLSTR.

Three safeguards stand out for borrowers. First, the margin cannot go up in the conversion: it may stay the same or be lower than in the current contract. Second, you would get around 60 days to decide. Third, the annex is entirely voluntary and refusal carries no sanctions: if you say no or simply do not reply, your contract keeps running on WIBOR, which will be published for legacy contracts until the end of 2036.

The government has dropped the earlier idea of forcing conversion by regulation. A corrective spread, an adjustment meant to even out the level difference between WIBOR and POLSTR (it could also be negative), would apply only in an emergency scenario where a statutory replacement has to be designated; the Financial Stability Committee judged that the 10-year phase-out makes it unnecessary. In practice, the voluntary annexes are meant to come without a corrective spread. Note that no bank is sending these annexes yet: banks are preparing to do so after the law enters into force. The head of the Polish Bank Association, Tadeusz Bialek, has called the reform "inevitable and irreversible".

What to do as a foreigner with a Polish mortgage

Right now: nothing. Your contract does not change automatically, and the reform itself gives no bank grounds to raise your rate. If the draft becomes law, expect a formal annex offer from your bank, in Polish. Use the roughly 60 days the draft would give you: have the annex translated or reviewed before signing, and verify two things above all, that the margin is not higher than in your current contract, and which option you are choosing, fixed or POLSTR.

Whether POLSTR wins depends on the rate cycle. Today it is about 0.25 percentage points below WIBOR 3M, and its monthly reset passes NBP rate cuts to your installment faster. The same mechanism works against you when rates rise. Before deciding, run your own numbers with our loan and mortgage calculators: even a quarter of a percentage point on a large balance changes the installment noticeably over a full term.

If you are only now shopping for a home loan, remember that from 2027 new contracts will not use WIBOR at all. POLSTR mortgages for consumers are not yet in bank offers: the only POLSTR-based product so far is a business overdraft launched by Bank Pekao on 6 November 2025, and PKO BP has announced POLSTR products in line with the NGR schedule. Compare current offers in our mortgage ranking and, if you are buying as a foreigner, see our guide to getting a 500,000 PLN mortgage in Poland as a foreigner.