Late-payment interest – work out the interest on an unpaid invoice
An unpaid invoice costs you interest for every day it goes unpaid. The calculator works out exactly how much late-payment interest you are owed and adds the statutory reminder and debt-collection fees, so you see the full amount to claim.
Work out late-payment interest
Enter the invoice amount, due date and when payment was made (or today’s date). The rate is the reference rate + 8 percentage points per the Swedish Interest Act – adjust the reference rate if Riksbanken has changed it.
The calculation uses simple interest (amount × rate × days/365). The reference rate is set by Riksbanken on 1 January and 1 July – check the current level at riksbank.se.
This tool gives an estimate and is an aid – not a finished calculation. Always check the result against drawings, applicable regulations, supplier data and your professional experience before giving a binding price, ordering material or using the file. ByggExp is not responsible for decisions made solely on the basis of the tool.
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How late-payment interest is calculated
Late-payment interest is simple interest calculated on the unpaid amount incl. VAT: amount × rate ÷ 365 × number of days. Per the Interest Act the rate is Riksbanken’s reference rate plus 8 percentage points.
Example: an invoice of 50,000 kr paid 30 days late, with a reference rate of 2% (late-payment interest 10%), gives 50,000 × 0.10 ÷ 365 × 30 ≈ 411 kr in interest.
The reference rate changes twice a year
Riksbanken sets the reference rate on 1 January and 1 July. Because the level changes, check the current reference rate and enter it in the calculator – then the late-payment interest is correct.
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Frequently asked questions about late-payment interest
- How high is the late-payment interest?
- Per the Interest Act it is the reference rate plus 8 percentage points, unless you have agreed another rate. If you have agreed a higher contractual rate, that applies instead.
- From which day is the interest counted?
- If you have a due date, interest runs from the day after the due date. Without a due date you may charge late-payment interest at the earliest 30 days after you sent the invoice or demand for payment.
- May I charge reminder and debt-collection fees?
- Yes. If it is stated in the agreement or invoice you may charge the statutory reminder fee (60 kr) and debt-collection fee (180 kr). Tick them in the calculator to add them to the total.
- Does the calculator cost anything?
- No, it is free and requires no account.