A late invoice is not just annoying. Work out what a slow-paying customer is actually costing you, once you count the cash tied up, the time spent chasing it, and the job it held up.
A late payment costs more than the invoice number suggests. There is the cost of that cash being tied up instead of working for you, the time you spend chasing it, and the knock-on cost if the delay held up starting your next job. Add them up and a "small" delay is often a real hit to your profit, not just an inconvenience.
What you are owed, and how late it is.
The time it took, and any work it held up.
A guide, not financial advice. Figures are estimates. Use your own overdraft rate or a sensible stand-in, and your own hourly rate.
Most trades track whether an invoice got paid. Far fewer track what it cost them to wait for it. That cash sitting unpaid is not free to you, it is money that could have covered next week's materials, paid a wage, or just sat in the business as a buffer. Every week it is late, it is quietly costing you.
A deposit up front does two things at once. It gets some of the job's cost covered before you have spent a cent on materials, and it filters out the customers who were never going to pay properly in the first place. If someone will not put down a deposit, that is useful information, not an inconvenience.
A friendly reminder on the due date, a firmer follow-up a week later, and a clear next step if it still has not landed, that is the whole playbook for most cases. Agree payment terms and any late-payment interest in writing before the job starts, so if you ever need it, it is not a surprise to either of you.