WIBOR, WIRON and POLSTR 2026 – what they are, how they affect your instalment, the reform
Author: Tacjana MasiukiewiczMortgages~12 min read
WIBOR is the benchmark on which the interest rate of most variable-rate mortgages in Poland depends. WIRON was supposed to replace it, but in 2025 the reform was redirected to a new benchmark – POLSTR. In May 2026 a key decision was taken: WIBOR 1M, 3M and 6M will be published until 31 December 2036, and from 2027 it should not go into new contracts. We explain what this means for your instalment – and show in numbers how the instalment changes with the benchmark.
Key facts
- The interest on a variable-rate loan = the reference rate + the bank's margin. The margin is fixed for the whole term of the agreement, the benchmark changes.
- As of 25 September 2026: WIBOR 3M – 3.86%, WIBOR 6M – 3.90%, POLSTR 1M Compounded Rate (Stopa Składana) – 3.55% (GPW Benchmark).
- The last day of publication of WIBOR 1M, 3M and 6M is 31 December 2036. Existing agreements still rely on WIBOR – there is no automatic switch to a new benchmark.
- The KNF expects that from 1 January 2027 banks will not conclude new agreements based on WIBOR. New loans are a fixed (periodically fixed) rate or a variable rate based on POLSTR.
- On a loan of 500 thousand zł over 25 years every 1 percentage point of the benchmark is about 310–330 zł of instalment a month (our calculation below).
WIBOR, WIRON and POLSTR – what are they?
WIBOR (Warsaw Interbank Offered Rate) is the rate at which banks are ready to lend money to each other for a set term: 1 month (1M), 3 months (3M) or 6 months (6M). It is determined by GPW Benchmark SA – an administrator of reference benchmarks supervised by the KNF. In mortgages WIBOR 3M (interest updated every quarter) and WIBOR 6M (every half-year) were most often used.
WIRON is an index based on actual overnight deposit transactions (for one day). In 2022 the National Working Group on benchmark reform (NGR) chose it as WIBOR's successor. GPW Benchmark still publishes it (24 September 2026: 3.071%), but it is no longer the target benchmark of the reform.
POLSTR (Polish Short Term Rate) is the current successor to WIBOR. In December 2024 the NGR Steering Committee chose a new index from the WIRF family (based on unsecured deposits of credit and financial institutions), on 24 January 2025 it gave it the name POLSTR, and since 2 June 2025 GPW Benchmark has officially determined it. It is a benchmark of the RFR type (close to a risk-free rate): the volume-weighted average rate of overnight deposit transactions in zloty. For loans, compounded rates are also published – POLSTR 1M, 3M and 6M.
| Benchmark | Value | Date of the benchmark | Role in loans |
|---|---|---|---|
| WIBOR 1M | 3.76% | 25.09.2026 | less often used in mortgages |
| WIBOR 3M | 3.86% | 25.09.2026 | the most popular in existing loans |
| WIBOR 6M | 3.90% | 25.09.2026 | the second most common in existing loans |
| POLSTR (overnight) | 3.593% | 24.09.2026 | the base index |
| POLSTR 1M Compounded Rate | 3.55055% | 25.09.2026 | recommended for new variable-rate consumer loans |
| POLSTR 3M Compounded Rate | 3.57316% | 25.09.2026 | – |
| WIRON | 3.071% | 24.09.2026 | the former candidate to succeed WIBOR |
The difference between WIBOR 3M and POLSTR 1M is today about 0.3 percentage points. This does not automatically mean a cheaper POLSTR loan – the bank sets the margin separately for each product, so compare the whole interest rate and the APR, not just the benchmark.
When will WIBOR disappear? The reform timetable (as of September 2026)
The first roadmap (2022) assumed replacing WIBOR with WIRON. After the target benchmark was changed to POLSTR, the NGR adopted a new roadmap (28 March 2025) and updated it on 30 June 2026. The most important dates:
| Date | What happened / will happen |
|---|---|
| 2 June 2025 | The start of the official determination of POLSTR and the POLSTR compounded rates |
| 12 September 2025 | The NGR adopts recommendations for new bank products based on POLSTR (including mortgages) |
| 21 November 2025 | The first issue of treasury bonds based on POLSTR |
| 22 December 2025 | The end of publication of WIBOR for the T/N and 2W tenors |
| 18 May 2026 | GPW Benchmark announces the cessation of WIBOR 1M, 3M and 6M from 1 January 2037; the KNF finds the procedure compliant with the BMR regulation |
| June 2026 | The Financial Stability Committee: no need to designate a replacement for WIBOR; the Ministry of Finance will not issue a regulation on the matter |
| 1 October 2026 | The end of publication of WIBOR O/N |
| 22 December 2026 | The first day without WIBOR 1Y (the KNF may extend the duty to publish by 12 months) |
| from 1 January 2027 | New agreements should not refer to WIBOR – the benchmark serves only to administer existing agreements |
| 31 December 2036 | The last day of publication of WIBOR 1M, 3M and 6M; wind-down on 1 January 2037 |
The change of course is worth noting. A few years ago people spoke of an "automatic replacement of WIBOR with WIRON" in all agreements under a regulation of the Minister of Finance naming a replacement. As of September 2026 that scenario is not being carried out: since WIBOR will be published for more than another 10 years, a statutory replacement is not needed. The KNF indicated that this period is to let financial institutions gradually change agreements – including agreements with consumers.
What does the reform mean for your WIBOR loan?
If you have a loan based on WIBOR 3M or 6M, you do not have to do anything today:
- The agreement works unchanged. The interest is still calculated as WIBOR + the margin from the agreement, and the bank updates it on the dates in the agreement (every 3 or 6 months).
- There is no automatic switch of the benchmark. By the end of September 2026 the NGR had adopted a recommendation on replacing WIBOR in existing agreements only for business clients (December 2025) and for discount products (May 2026). No recommendation has been published for private individuals' mortgages.
- A change requires an annex. The bank may propose moving to POLSTR or a fixed rate. Such a proposal is worth recalculating: how the instalment will change and whether the margin stays the same.
- A loan running longer than to 2036. In agreements with a long horizon the question of a replacement benchmark will return before 2037. Check in the agreement what it provides in case the benchmark ceases to be published.
The Mortgage Loan Act requires that when the reference benchmark changes the bank give you information at the latest together with the new repayment schedule (art. 31), and the benchmarks used must be understandable, accessible and verifiable (art. 32).
If you want to make your instalment independent of the benchmark right now, you have two routes: moving to a periodically fixed rate at your bank or refinancing at another. We describe the comparison of the options in the articles A fixed or variable mortgage rate and Mortgage refinancing in 2026.
WIRON or POLSTR instead of WIBOR in a new mortgage
If you are taking a loan now, a variable-rate loan based on WIRON will no longer appear: new variable offers will be based on POLSTR. The NGR recommendation of 12 September 2025 provides for consumers:
- A variable-rate loan – interest based on the POLSTR 1M Compounded Rate benchmark with a one-month interest period. The interest therefore changes every month, not every quarter as with WIBOR 3M.
- A loan with a periodically fixed rate – after the fixed-rate period ends you may agree with the bank the next fixed-rate period or move to the variable rate from the agreement (recommended: POLSTR 1M Compounded Rate).
- Advance information – the value of the POLSTR 1M Compounded Rate is known before the interest period begins, so the bank can tell you the instalment before the payment date.
The practical difference: WIBOR is a rate for a term (e.g. 3 months), so it partly reflects expectations about rates in that period, while POLSTR reflects the overnight rates realised in the past period. So POLSTR reacts to Monetary Policy Council decisions with a slight delay, but without "anticipating" them. It is also worth remembering that most new mortgages are in any case granted today with a periodically fixed rate – according to the NBP (AMRON data) in Q1 2026 that was about 64%.
Not sure whether to choose a fixed rate or a variable one on POLSTR? Book a consultation with a mortgage expert – we will compare offers from several banks and recalculate the instalment in both variants for your loan amount.
WIBOR and the loan instalment – how much does 1 percentage point change?
The assumptions: a loan of 500 thousand zł over 25 years (300 instalments), equal instalments, a bank margin of 2.0 percentage points (assumed for the example – real margins depend on the bank, the LTV and your profile). The benchmark is WIBOR or POLSTR – for the instalment it does not matter which, its value is what counts.
| Benchmark | Interest (benchmark + 2 percentage points) | Monthly instalment | Total interest over 25 years |
|---|---|---|---|
| 3.55% (POLSTR 1M, 25.09.2026) | 5.55% | approx. 3,085 | approx. 426 thousand |
| 3.86% (WIBOR 3M, 25.09.2026) | 5.86% | approx. 3,179 | approx. 454 thousand |
| 4% | 6% | approx. 3,222 | approx. 466 thousand |
| 5% | 7% | approx. 3,534 | approx. 560 thousand |
| 6% | 8% | approx. 3,859 | approx. 658 thousand |
Conclusions from the table:
- A rise in the benchmark from 4% to 5% raises the instalment by about 312 zł, and from 5% to 6% by a further 325 zł. The higher the rates, the more heavily each point weighs on the budget.
- The difference between today's WIBOR 3M and the 6% scenario is about 680 zł a month, that is more than 8 thousand zł a year.
- That is why the bank assesses borrowing capacity with a variable rate with a buffer of at least 2.5 percentage points (KNF Recommendation S) – more in the article Borrowing capacity 2026.
You will find instalment tables for other amounts (600, 700, 800 thousand zł) and terms of 30–35 years in the article Mortgage instalment – tables and examples.
An example on prices from our offer
According to data from the TM Invest offer, as of 27 September 2026, the median price of a 2-room flat in Wrocław is 662,405 zł, and in Warsaw 755,824 zł. With a 20% deposit the loan is about 530 thousand zł and about 605 thousand zł respectively. With a margin of 2 percentage points and a term of 25 years the instalment looks like this:
| Flat (median, 2 rooms) | An 80% loan | Instalment at today's WIBOR 3M (5.86%) | Instalment if the benchmark +1 pt | Instalment if the benchmark +2 pts |
|---|---|---|---|---|
| Wrocław – 662,405 | approx. 530 thousand | approx. 3,370 | approx. 3,700 | approx. 4,040 |
| Warsaw – 755,824 | approx. 605 thousand | approx. 3,845 | approx. 4,220 | approx. 4,610 |
You will find current flats in these price ranges in the catalogue: new flats in Wrocław and new flats in Warsaw. How to go through the whole process – from borrowing capacity to the release of tranches – we describe in the guide A mortgage in Poland step by step.
Frequently asked questions
What is WIBOR 3M today?
According to GPW Benchmark, WIBOR 3M on 25 September 2026 was 3.86%, and WIBOR 6M 3.90%. The fixing takes place on working days at 11:00 – before deciding, check the latest value on gpwbenchmark.pl.
When will WIBOR disappear?
WIBOR 1M, 3M and 6M will be published until 31 December 2036, and wound down on 1 January 2037. From 1 January 2027 it should not be used in new agreements, but existing loans will still refer to it.
Will my loan be automatically moved to WIRON or POLSTR?
As of September 2026 – no. The Financial Stability Committee found that there is no need to designate a replacement for WIBOR, and the Ministry of Finance will not issue a regulation on the matter. A change of benchmark in your agreement therefore requires agreement with the bank (an annex).
POLSTR – what is it in simple words?
It is the average interest on one-day deposits that financial institutions actually conclude on the interbank market in zloty. Unlike WIBOR it rests on real transactions in the past, not on declared rates for the future. In loans its compounded rate for a month (POLSTR 1M) is used.
Will a loan on POLSTR be cheaper than on WIBOR?
The benchmark itself is today about 0.3 percentage points lower, but the cost of a loan is decided by the sum of the benchmark and the margin, and banks may price margins differently. Compare the nominal interest and the APR of the whole offer – we describe the rules of comparison in the article Which bank for a mortgage.
Is it worth moving to a fixed rate now?
It depends on what fixed rate the bank proposes compared with today's variable interest and how much variability of the instalment you can bear.
Summary
Benchmark reform in Poland has gone a different way from what was assumed a few years ago: instead of WIRON, WIBOR's successor is POLSTR, and instead of a quick replacement in all agreements – more than 10 years of winding down. Existing loans on WIBOR work unchanged, and new loans from 2027 are a fixed rate or a variable rate on POLSTR.
Planning a loan, or wondering what to do with your current one? Book a consultation with a mortgage expert – we will compare offers from several banks (a fixed rate, POLSTR, WIBOR until the end of 2026) and show how the instalment will change under different rate scenarios.
Legal status as of September 2026, benchmark values of 24–25 September 2026. The calculations are indicative and are not an offer or legal or financial advice – the credit decision is taken by the bank.
Sources
- GPW Benchmark SA – WIBOR, POLSTR and WIRON values (24–25 September 2026) and the announcement of 18 May 2026 on the cessation of WIBID and WIBOR (in Polish).
- KNF, Cessation of the fixing tenors 1M, 3M, 6M WIBOR – 31 December 2036 (18 May 2026; in Polish).
- NGR, Update of the roadmap for reform of reference benchmarks (30 June 2026; in Polish) and the announcement of 20 May 2026.
- NGR, the choice of the name POLSTR and the start of determining POLSTR (2 June 2025; in Polish).
- NGR, Recommendation for new sales – bank products – POLSTR (12 September 2025; in Polish).
- Mortgage Loan Act and the Act on Supervision of Mortgage Credit Intermediaries and Agents – consolidated text, Journal of Laws 2025 item 720 (art. 29, 31, 32).
- NBP, Information on home prices and the situation on the real estate market in Q1 2026 – the share of fixed-rate loans.
- Flat prices: the TM Invest catalogue of developments, as of 27 September 2026.
