Think about a collection agency as an extreme step and only as a last resort after you have contacted the client multiple times and sent them late payment follow-up reminders. If they have repeatedly ignored the client payment reminders and not reverted to you with a meaningful course of action, it may be time to take extreme measures.  Try to get the payment processed with calm and professional communications and follow up till a month past the due date. If they are still no show, engage collection agencies to help you recover debts in exchange for a fee.