Document text
[Date]
[Client name]
[Client address]
Re: Late payment charge on invoice no. [Invoice no.]
Dear [Client name],
Invoice no. [Invoice no.] for [Total due] was due on [Due date] and remains unpaid. Under [Clause] of our [Agreement], late payments carry a charge of [Agreed rate].
Invoice amount [Total due]
Late charge to [Date] [Late charge]
Please pay the invoice and the late charge by [New date], using [Payment details].
Sincerely,
[Your name]
Use this letter only if a written agreement sets the rate: Civil Code Art. 1956 says interest is due only if stipulated in writing, and Art. 1229 lets courts reduce a penalty that is too high. No such clause: skip it and send the demand letter. Checked 01.11.2026. Not legal advice.