Installment vs. Instalment
“Installment” and “instalment” are standard regional variants. “Installment” is the usual U.S. spelling, while “instalment” is chiefly British usage.
Use “installment” in U.S. English and “instalment” in British English, unless your house style chooses differently.
Key details
Choose the right form
| Audience / style | Preferred spelling | Meaning |
|---|---|---|
| US English | installment | Usual US spelling. |
| British English | instalment | Chiefly British spelling. |
| House style with a specified dictionary | follow house style | The spelling difference does not change the noun’s meaning. |
Quick tests
Regional-style test
Is the document following a US or British spelling convention?
If yes: Use the spelling expected by that convention.
If no: If no convention is specified, choose one standard form and remain consistent.
Caveat: This is a regional spelling choice, not a distinction between different types of payments or parts.
Examples
US style: The final installment is due in June.
“Installment” matches the usual US spelling.
UK style: The final instalment is due in June.
“Instalment” matches the chiefly British spelling.
Further guidance
Core difference
The two spellings normally represent the same noun; the difference is regional.
Usage Boundary
Choose the spelling expected by the audience or house style and keep it consistent.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Installment — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · US spelling evidence for installment
- Instalment — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · Mainly UK spelling evidence for instalment