Good day recently I have had several other small companies ask what I do about late on non payment of invoices. First every client receives a quote with the project clearly outlined with the quote is my payment schedule this is normally 7days after report is submitted or completion of the project. The invoice does not state 7 day but ask for payment before a certain day (7days) I then wait 10 days of the fee is not received I send a e-mail outlining what will happen next after 7 days I send the invoice to a debt recovery company this has so far worked with all invoices paid, I hope this helps you please contact if you would like to see a sample of e-mail that I send