Billing
Dunning Emails That Collect Without Losing the Client
Most overdue invoices aren't refusals to pay. They're an expired card, a missing PO number, or an invoice sent to someone who left — and the tone of the first reminder decides how the rest goes.
Collections processes are usually designed for the debtor who will not pay, and then applied to everyone. That is backwards. The large majority of overdue invoices are administrative accidents, and treating an accident like a default costs goodwill for no gain in recovery.
Separate the three populations
• Cannot pay yet — a cash flow problem, and a payment plan collects more than a demand.
• Did not receive it properly — wrong contact, missing PO, invoice failed a portal validation.
• Will not pay — a dispute about the work, or a deliberate stretch of terms.
Only the third needs escalation, and it is the smallest group. The second is the largest, and it is fixed with information rather than pressure — which is why the first message should ask a question, not make a demand.
A sequence that works
• Three days before due — a courtesy note with the invoice attached and the payment link. Prevention beats collection.
• Day one overdue — short, warm, assume an oversight, ask whether anything is missing.
• Day seven — restate the amount and due date, offer to re-send in whatever format their system needs.
• Day fourteen — a phone call. This is the step that actually collects, and the one most often skipped.
• Day thirty — a firm written notice naming the consequence, from someone senior.
• Day forty-five — stop work or escalate, as your terms provide.
The phone call at day fourteen collects more than every email in the sequence combined.
Remove the friction you control
Before blaming the client, check your own invoice. Does it carry their PO number, the right entity name, the correct billing contact, a breakdown that matches what they approved, and a payment method they can actually use without raising a new vendor record? A meaningful share of late payments are caused by an invoice that could not be processed as sent.
Keep the relationship owner informed, not involved
The account manager should know an invoice is overdue before the client mentions it, and should not be the one chasing it. Collections from the relationship owner puts the commercial relationship and the payment demand in the same conversation, which weakens both. Finance chases; the relationship owner is briefed and can intervene by exception.
Measure the cause, not just the days
Days sales outstanding tells you that you have a problem. Tagging each late invoice with a reason code tells you which one. If a third of them are 'PO number missing', the fix is a change to the order intake process, and no amount of better-worded reminders will find it.
The day-fourteen call is the whole article. We resisted it for years because it felt confrontational, then tried it for a quarter and DSO dropped by nine days. Nobody was offended. Most people were apologetic.
Would add a step zero: check the invoice actually arrived in their AP portal. We lost a fortune to invoices that were 'sent' by email to a mailbox that stopped being monitored in 2024.
Disagree slightly on keeping the account manager out of it. In a small client base they often know the actual reason within one message, and going through finance first just adds a week.