When you see two offers tagged „interest rate 9%", one can come out almost twice as expensive as the other. The deciding number is RRSO — the Polish APR. It takes the nominal rate, adds the arrangement fee, admin charges and any mandatory insurance, and pulls them all into a single annual figure.
RRSO is calculated using the formula in Annex 4 of the Polish consumer credit law. Every regulated institution has to compute it the same way, so the comparison is honest.
A worked example that makes it click
Loan A: nominal rate 8%, arrangement fee 5%. Loan B: nominal rate 10%, no fee.
On 30 000 PLN over 48 months, the RRSO of loan A lands above 13%; the RRSO of B sits near 10.5%. The „lower" headline rate turned out to be 2.5 points more expensive per year. This happens all the time.
What RRSO does not tell you
RRSO does not include optional insurance (life, job-loss cover) and is calculated assuming „no late payments". Miss a payment once and the real cost goes up. Sign an optional policy at the end of the application and it sits outside the RRSO you saw at the start. Ask for the cost breakdown in writing before you sign.
How we sort by it
Every offer in the comparison is sorted from lowest to highest RRSO. Cheapest first, no paid placement. If you want to sort by amount, term or rating, the selector is in the top right.
When RRSO misleads
Even RRSO has its weak spots. Three cases where the number does not paint the full picture. A loan with a very short promotional period: the bank offers 0% RRSO for the first 3 months, then the standard rate. RRSO averages both windows, so the figure looks lower than the real post-promotion price.
A foreign-currency loan (CHF, EUR): RRSO is calculated assuming a stable exchange rate, but currency risk can add ten-plus percent over a few years. CHF borrowers from 2005–2010 know this pattern best — the signed RRSO was 4%, the real 15-year cost came in closer to 15%. A long-term variable-rate loan: RRSO is calculated on today's WIBOR. One NBP decision and it rises by 1–2 pp.
A practical rule of thumb
If the RRSO gap between two offers is under 0.5 pp, check the rest: early-repayment flexibility, service availability at your bank, mobile app quality. If the gap crosses 1.5 pp, RRSO is effectively decisive — the rest does not matter at loan scale.