Retainer clients should pay for the month before it starts, not 30 days after it ends.
For US consultants and agencies on monthly retainers: invoice around the 20th for next month, due by the 1st. Say on the invoice what the month covers (hours or deliverables) and what happens to unused hours.
Net 15 and Net 30 only help if the client can see them on the invoice.
For US consultants and agencies: write the term and the due date on every invoice, then keep every reminder pointing at that same date. No "whenever you can" wording. No new deadline in the chase email.
Most overdue emails fail because the client still has to hunt for how to pay.
For US consultants and agencies: put one pay link in every reminder. Same thread as the invoice. Invoice number, exact amount, original due date, then the link. No scavenger hunt through old PDFs.
