Pro Forma vs. Proforma vs. Pro-Forma
For the general English expression, major dictionary treatment favors the two-word form “pro forma.” Cambridge also records “proforma invoice” as a variant within that business compound, so the closed form should not be generalized into a universal spelling rule.
Use “pro forma” as the general form. “Proforma” is recorded in some compounds such as “proforma invoice”; do not assume “pro-forma” or “proforma” is the universal default.
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| general Latin-derived expression/adjective | pro forma | Use the open two-word form as the general default. |
| established compound such as invoice terminology | proforma in documented compounds | The closed form is recorded in some compounds, including “proforma invoice.” |
| hyphenated pro-forma | do not assume it is the universal default | Verify the established term or house style before using the hyphenated form. |
Quick tests
Meaning / construction test
Are you using the general expression rather than an established closed compound?
If yes: Use “pro forma.”
If no: If the term is an established compound such as “proforma invoice,” the closed form may be documented; verify before choosing a hyphenated form.
Caveat: This is a three-form spelling choice, not a binary test. “Pro forma” is the general form, “proforma” is documented in some compounds, and the evidence does not make “pro-forma” a universal default.
Examples
The board approved the proposal pro forma.
The general expression uses the open form.
The supplier sent a proforma invoice.
The closed form is documented in this compound.
Check the established term before writing “pro-forma.”
The hyphenated spelling should not be treated as the universal default.
Further guidance
Compound Boundary
Cambridge separately records “proforma invoice” as a variant, showing that the closed form can occur in established compound usage rather than serving as a blanket replacement for “pro forma”.
General Form
For ordinary uses of the Latin-derived expression in English, “pro forma” is the clearest default because that is the dictionary headword.
Hyphen Boundary
A hyphen may appear in particular edited compounds or house styles, but the main dictionary headword does not make “pro-forma” the general default.
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.
- Pro forma — English meaning (opens in a new tab)Cambridge University Press · Dictionary headword, word class and current usage of “pro forma”
- Pro forma invoice — English meaning (opens in a new tab)Cambridge University Press · Dictionary attestation of “pro forma invoice” and the recorded “proforma invoice” variant