What is the due date on the invoice? Typically you would send an initial invoice with a +30 day (ish) due date. The client would pay as close to the 30 days as

What is the due date on the invoice? Typically you would send an initial invoice with a +30 day (ish) due date. The client would pay as close to the 30 days as they could because it is better for their cash-flow. If they failed to pay after 30 days you would send them an "invoice overdue" letter. When you're comfortable that had arrived you could then call/e-mail them essentially asking them about payment on the initial invoice. If this "invoice overdue" notice isn't paid within short order (20~30 days) then you should send them a "final notice" and this should specifically indicate that the next step is court/collections. Everything should have the date of issue, the date it is due (e.g. +30 days, immediately, etc), and you should not do too much "extra work" beyond sending out letters and the occasional phone call (as this implicitely costs you money). If they still haven't paid after the final notice then you can either hire a collections agency (who will take a % cut) or attempt to sue them (and hope they don't declare bankruptcy).