Judgment interest calculator (8% on judgment debts)
calculate_judgment_interestWorks out simple interest at 8% a year on a judgment debt in England and Wales, from the date of judgment (or a date the court ordered, or in the County Court a date for payment in the judgment) to the date you choose. High Court: any judgment (Judgments Act 1838 s.17); no rule fixes how part payments are applied, so the default is interest first, a rule of thumb the Court of Appeal accepted as fair, with the debt-first total alongside. County Court: only judgments of £5,000 or more or for a Late Payment Act qualifying debt, with the exceptions in the County Courts (Interest on Judgment Debts) Order 1991: consumer credit and suspended possession orders carry none, payments go to the debt first, County Court enforcement that produced a payment stops it, and an attachment of earnings or administration order suspends it while in force. Flags interest more than six years old (Limitation Act 1980 s.24(2)). Leap years per Lomas v Burlington. Not for interest on costs (use calculate_interest_on_costs) or interest before judgment.
Tool call template
Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {
"court": "<court>",
"judgmentDate": "<judgmentDate>",
"sum": "<sum>"
},
"name": "calculate_judgment_interest"
}
}Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| cca | No | County Court: the claim was under an agreement regulated by the Consumer Credit Act 1974 (no interest). | |
| lpa | No | County Court: the judgment is for a qualifying debt under the Late Payment of Commercial Debts (Interest) Act 1998, so it carries interest under £5,000. | |
| spo | No | County Court: a suspended possession order for a landlord or mortgagee of a dwelling (no interest). | |
| sum | Yes | The judgment debt: everything the judgment orders to be paid as a sum, including any costs stated in it, in pounds (e.g. "12500.50"). | |
| leap | No | "lomas" (default) divides a year containing 29 February by 366; "365" uses 365 throughout. | |
| aoeTo | No | County Court: the date that order ended, if it has. | |
| court | Yes | High Court or County Court. | |
| payBy | No | County Court: the date for payment the judgment set, if any (1991 Order art 3(a)). | |
| aoeFrom | No | County Court: the date an attachment of earnings order that produced nothing, or an administration order, came into force. If attachment of earnings produced a payment, give its start as enforcementFrom instead. | |
| endDate | No | The date to calculate interest to (defaults to today). | |
| payments | No | Payments since the judgment, each with a date and an amount. | |
| startDate | No | Where customStart is true: the date interest runs from. | |
| paymentsTo | No | High Court only: apply payments to interest first (the default: no rule fixes the order, and the Court of Appeal accepted this rule of thumb as fair in Evonik UK Holdings Ltd v HMRC [2025] EWCA Civ 1392) or to the judgment debt first. County Court payments always go to the debt first. | |
| customStart | No | The court ordered interest to run from another date. | |
| instalments | No | County Court: the judgment is payable by instalments (not calculated). | |
| judgmentDate | Yes | The date judgment was given for the sum; where damages were assessed later, the date of that judgment. | |
| enforcementFrom | No | County Court: the date enforcement proceedings in the County Court were taken, if they produced a payment. |