Pause the work
How to pause work until an invoice is paid
Send this when an open invoice is old enough that starting more work would be a gift. The note says the work is paused. It does not pretend to be a lawyer.
Pausing is a business decision you can make on your own. You stop new work, revisions, and meetings that move the project forward. You say the amount, the invoice, and that the work starts again when the payment lands.
Don’t call it a final legal notice if it isn’t one. Don’t threaten a lawsuit you won’t file, and don’t mention a collections agency or their credit. Those lines escalate a late invoice into a fight, and they can be wrong for where you and the client live. Saying you will review all of your options, including legal ones, is enough for this note. If you actually need a demand letter, use a lawyer.
Send it when a promised date has failed twice, or when they ask for new work while an older invoice is still open. Sending it three days after the due date trains them to ignore you.
If they pay, restart the work the day it lands and say so in one line. If they don’t, you already stopped, and the note already said you will review all of your options, including legal ones. You don’t need a fourth email that repeats the third.