Late Payment Interest Claim: UK, EU, Germany by ReadyStack

Work out what you may legally add to an overdue B2B invoice: statutory interest at the locked half-year rate, plus the automatic fixed compensation almost every invoice forgets.


Click Add to Firefox on this page. Nothing to unzip, no developer mode - the free version runs right away.

• Half-year rate lock — Applies the reference rate in force on 31 December or 30 June before the invoice fell late, which is the rate the statute points at - not the rate in force today.
• Fixed compensation tier — Adds the automatic recovery sum for the size of the debt: 40, 70 or 100 pounds in the UK, 40 euro in the euro area. It is owed even if the contract says nothing.
• German nine-point margin — Uses the nine percentage points that section 288(2) BGB gives on German B2B debts, instead of the eight-point EU minimum that general-purpose calculators apply everywhere.
• Shortfall against the shortcut — Shows in money what the invoice loses if the fixed sum is left off and the flat eight-point margin is used - the two mistakes that make up almost every under-billed claim.
• Claim ledger export — With a licence key: downloads the worked figures as a .csv row you can keep, hand to your accountant, or attach to a letter before action.

| You type | |
|---|---|
| Sum owed on the invoice | default 8400 |
| Already paid off | default 0 |
| Days past the due date | default 74 |
| Which law applies | default uk |
| When it became late | default 2026-H2 |

| It answers | |
|---|---|
| Statutory rate | |
| Reference rate used | |
| Interest per day | |
| Interest so far | |
| Fixed compensation | |
| Total you can invoice | |
| Lost if you skip it | |

Permissions requested: storage, downloads


Free: the calculation in the popup, no key, no limit. Full version ($60): download the result as .csv - one licence key per person or team seat. Get it: https://getreadystack.com/api/buy/cl/polar_cl_NYu4gG5rKHitEHGJPU4Bpobq2abqtHAz8vWsW3spztQ


When you use the tool, the extension sends one anonymous count a day (the tool’s name only — no inputs, no personal data). Turn it off on the first page after install. Firefox asks first and sends nothing unless you allow it. A licence key is checked with the payment provider (Polar) only when you enter one.