The statutory interest-rate almanac · Guides

Guides

The rates on this site are only useful if you know what they mean. These plain-English guides explain how interest on judgments, unpaid tax, and late commercial payments actually works — then hand you the calculator to run your own numbers.

Post-Judgment Interest: What It Is and How It Accrues

Post-judgment interest accrues on a judgment from entry until it's paid. Learn the federal §1961 rule, how states differ, simple vs. compound, and how to calculate it.

Prejudgment Interest, Explained

Prejudgment interest compensates for the wait between a loss and judgment. Learn why it's limited to liquidated claims, how the rate is set, and when it accrues.

How to Calculate Judgment Interest

Learn to calculate judgment interest step by step: find the governing rate, lock it to the judgment date, apply simple vs. compound, and do the daily math.

How IRS Interest Rates Work Under §6621 and §6622

A plain-English guide to IRS interest rates: how §6621 sets the federal short-term rate plus a category spread, quarterly resets, and daily compounding under §6622.

Late Payment Interest on Commercial Debts: The UK and EU Rules

How statutory late payment interest works on overdue B2B invoices in the UK and EU: the base-rate-plus-8 formula, fixed compensation, and how to claim it.

Statutory Interest: A Plain-English Guide

Statutory interest is a rate set by law, not by your contract. Learn how it is determined for judgments, unpaid tax, and late payments across the US, UK, and EU.

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