The first significant late payment I experienced left me paralysed for two weeks. I didn't know what to do. I didn't want to come across as aggressive with a client the relationship had been good with. I kept putting off the follow-up until tomorrow. Meanwhile, the invoice stayed unpaid.
What I've learned since: waiting solves nothing and often makes things worse. A client who pays late won't spontaneously fix the situation if they don't receive a signal that you're tracking it.
The protocol I now follow is simple and non-negotiable.
On the due date: if the invoice hasn't been paid on the agreed day, I send a short, neutral email. "I notice invoice X hasn't been settled by its due date. Could you confirm everything is in order?" No accusation. Just a fact and a question.
Seven days later: if no response or no payment, a second, more direct follow-up with a reminder of the amount and a new deadline.
Fifteen days later: a phone call. Emails are easy to ignore. A call is less so.
Thirty days later: a formal notice. At this point, the relationship is already compromised - you might as well have a document that protects your rights.
What I've learned over time: most late payments aren't malicious. They come from poor organisation on the client's side, an internal approval chain that drags, or a simple oversight. A firm but neutral follow-up resolves most situations.
Prevention is still better than treatment. An upfront deposit, short payment terms, payment on delivery for new clients - these conditions drastically reduce late payments before they happen.
Not following up on an unpaid invoice out of fear of upsetting a client means paying yourself less than you're owed. That's not politeness. It's a concession nobody asked you to make.