You finished the job six weeks ago. The GC signed off, the invoice went out that Friday, and the terms were net-30. It's day 41 now, and the money still isn't in the account. Nobody said no. Nobody said anything at all.
This is the quiet way field-service and supply shops lose real money. Not to deadbeats, usually, but to invoices that sit in someone's inbox behind forty other emails, waiting for a busy person to remember you exist. Property managers, general contractors, and facilities teams tend to pay when they're prompted, and the shops that prompt first tend to get paid first.
The hard part is the follow-up itself. Calling to ask about your own money feels awkward, so it slides to next week, and next week it slides again. Meanwhile you're floating payroll and material costs on work that's already done and signed for. The fix isn't a tougher attitude. It's a schedule that runs the routine nudges for you, so the only calls you make are the ones that actually need your voice.
Net-30 usually means net-45
The due date is a starting point, not a promise. On the commercial side, your invoice has to clear a chain: it gets received, matched against a purchase order or a signed work authorization, approved by whoever okayed the job, then queued in a payment run that might only happen twice a month. Miss the run by a day and you've waited two more weeks through no fault of your own.
That's why aging matters more than the due date. "Aging" just means how many days old an unpaid invoice is, counted from the day you sent it. A steady shop watches the buckets: current, 1 to 30 days over, 31 to 60, and the ugly 60-plus. Most invoicing tools (QuickBooks, Xero, Jobber, ServiceTitan, and the like) build this report for you automatically. The number that should worry you isn't one late invoice. It's a growing stack in the 31-to-60 column, because that's money aging toward the point where collecting it gets genuinely hard.
The three-step reminder sequence
Here's the backbone. You set it up once, and it runs on every invoice without you thinking about it. The days are counted from the invoice date, and you can shift them for net-60 accounts.
- Day 15, the soft check-in. A short, friendly note that just confirms the invoice landed and is being processed. Half the time a late invoice is one that never got entered into the customer's accounts-payable system, and this catches that early while it's still easy to fix.
- Day 30, the firm reminder. The invoice is now due or just past due. This one states the amount, the due date, and a plain question: where does it stand in your next payment run? Polite, specific, no apology.
- Day 45, the escalation flag. This one doesn't go to the customer. It goes to you. The system pulls the still-unpaid invoice out of the pile and puts it on a short list so you can decide whether to call, pause new work, or loop in whoever signed the job.
The mechanics are simpler than they sound. Your invoicing tool already knows the invoice date, the balance, and the contact email. A small automation checks the aging report each morning, finds anything that hit day 15 or day 30 overnight, and sends the matching email from your business address. Anything at day 45 with a balance still owing gets flagged to you instead of the customer. Some tools do a version of this out of the box under "payment reminders," and the gaps get filled with a connector like Zapier or Make, or a light custom setup if your stack is fussy.
What to actually say
Tone does the heavy lifting here. You want to read like a shop that keeps good books, not one that's sweating the rent. Keep each message a few lines, always include the invoice number and amount, and always attach the PDF again so nobody has to go digging.
A day-15 note can be as plain as: "Hi [name], just confirming your team received invoice #1042 for the rooftop unit work at [property], dated [date] and due [date]. Happy to resend the PDF or a W-9 if AP needs anything to process it."
By day 30, tighten it up: "Invoice #1042 for $4,180 was due [date] and still shows unpaid on our end. Could you let me know where it sits in your next payment run?" That question does real work, because it assumes payment is coming and just asks about timing, which is a much easier thing for the other person to answer.
One caution on automation. Send these from a real, monitored inbox, not a no-reply address, because plenty of replies are genuinely useful ("resend to our new AP email," "we never got the PO number"). If those replies bounce into a void, your polite sequence turns into noise, and noise is how you train a customer to ignore you.
When to put the automation down and call
Automation is great at the routine nudge and terrible at judgment. It'll happily email a customer for the fourth time about an invoice that's stuck on a dispute nobody told it about, which makes you look like you're not paying attention. So draw a clear line: the sequence handles days 1 through 44, and a human handles anything that reaches the day-45 flag.
Pick up the phone when any of these show up:
- An invoice hits day 45 with no reply to either email. Silence past day 45 isn't a scheduling delay anymore, it's a signal.
- The same customer has two or more invoices aging at once. That's a pattern, and patterns are worth a direct conversation before the number gets bigger.
- A reply raises a dispute, a missing PO, or a "we thought that was covered under the contract." Those get solved by a person in five minutes and by email in five days.
- It's a big-ticket invoice, or a customer you want to keep for years. Relationship accounts deserve a call, not a nudge.
When you do call, keep it short and warm. You're not accusing anyone. You're a vendor checking on a payment and offering to fix whatever's holding it up. "Wanted to make sure invoice #1042 didn't get stuck somewhere, is there anything you need from me to get it into the next run?" gets you paid far more often than a stern letter does, and it keeps the door open for the next job.
Worth doing this week
You don't need to rebuild your billing to start. A few small moves this week will move money that's already owed to you.
- Pull your aging report today and read the 31-to-60 and 60-plus columns out loud. That total is the size of the problem, and most owners are surprised by it.
- Write your three messages once (day 15, day 30, day 45 internal flag) and save them as templates. Keep them short and reuse them.
- Turn on whatever payment-reminder feature your invoicing tool already has, and set the timing to match the sequence.
- Make sure reminders send from an inbox a human checks, so useful replies actually reach you.
- Put a standing 20-minute slot on your calendar, same time each week, to work the day-45 flag list by phone. That's the part no software should do for you.
Set up right, the routine follow-up just happens on schedule, and the awkward part shrinks down to a couple of calls a month instead of a chore you keep dodging. If you'd rather have someone wire the sequence into your invoicing tool so it runs quietly in the background, that's the kind of thing we help Houston shops set up at AI Agency Houston.