Invariably, at some point in their careers, translators and interpreters will have outstanding invoices that do not get paid in a timely manner. This post on Translation Times gives some tips for using the telephone for reminding clients of outstanding invoices.

Here are some guidelines to keep in mind:

• Be friendly, but firm. Give the other person the benefit of the doubt, especially if this is the first time you have an issue with the customer.
• Don’t threaten anyone. Be polite and accommodating — it’s easier to get paid this way.
• Offer solutions, including sending the invoice again via the postal service, etc.
• Ask to be added to the customer’s vendor database to provide future glitches in the payment process.
• Be gracious. This might very well be an isolated incident and this customer might turn out to be a superstar long-term client (that’s happened to us).

See: Translation Times