The work is done. The customer is happy. Now you need to get paid.
For a lot of HVAC contractors, invoicing is the part that gets pushed to "later." You're tired after a day of installs and repairs, and writing up invoices at 9 PM on the couch isn't anyone's idea of fun. So invoices go out late, or they're missing details, or they don't go out at all until someone asks.
Late invoices lead to late payments. Incomplete invoices lead to disputes. And the HVAC businesses that struggle with cash flow usually don't have a revenue problem. They have a collections problem that starts with sloppy invoicing.
What goes on an HVAC invoice
A complete invoice needs these sections. Skip any of them and you're creating an excuse for the customer to delay payment.
Your business info
Business name, address, phone, email, license number. If you're registered for sales tax, include your tax ID. This goes at the top. It looks professional and it's legally required in most states.
Customer info
Name, service address (not always the same as billing address), and phone number. For commercial customers, include a PO number if they gave you one. Accounts payable departments will reject invoices without the PO number, and you'll wait an extra 30 days for no reason.
Invoice number and date
Sequential invoice numbers. Doesn't matter if it's INV-001 or 20260226-01 or however you want to format it. Just make each one unique. This is how you track what's been paid and what hasn't.
Work performed
This is where most HVAC invoices fall short. "AC repair - $650" tells the customer nothing. Try this instead:
| Description | Qty | Rate | Amount |
|---|---|---|---|
| Diagnostic service call | 1 | $129.00 | $129.00 |
| Contactor replacement (Honeywell DP2030A) | 1 | $85.00 | $85.00 |
| Capacitor replacement (45/5 MFD) | 1 | $92.00 | $92.00 |
| Labor, AC repair (1.5 hrs) | 1.5 | $140.00 | $210.00 |
| Subtotal | $516.00 | ||
| Tax (8.25%) | $14.63 | ||
| Diagnostic fee credit | -$129.00 | ||
| Total due | $401.63 | ||
The customer can see exactly what they're paying for. No ambiguity, no "what was this charge for?" phone call three weeks later. And notice the diagnostic fee credit. If you charge a service call fee that gets applied to the repair, show it clearly. Customers appreciate the transparency and it reinforces the value of that upfront fee.
Payment terms
When is the money due? "Due upon receipt" is standard for residential work. "Net 30" is common for commercial. Whatever your terms are, print them on every invoice. If you charge a late fee, state it here: "Invoices unpaid after 30 days are subject to a 1.5% monthly service charge."
Will most people pay the late fee? Honestly, no. But having it on the invoice gives you leverage in follow-up conversations and filters out the customers who were planning to pay "whenever."
Payment methods
List every way the customer can pay you. Check, credit card, Venmo, Zelle, bank transfer. The more options you offer, the faster you get paid. If you can take a card on the spot when you finish the job, even better. Collecting at completion is always faster than invoicing later.
The "invoice same day" rule
Here's the single biggest change you can make: send the invoice the same day you finish the job. Same day. Not tomorrow, not this weekend, not when you get around to it.
Why? Two reasons. First, the customer's memory is fresh. They remember what you did, they're grateful the AC works again, and they're most likely to pay immediately. By next week, you're just another bill in the pile.
Second, it's a cash flow issue. If you finish a job on Monday and invoice on Friday, you've already given the customer a free four-day loan. If they take two weeks to pay after that, you're three weeks out from the work. Do that across 15-20 jobs a month and you're always chasing money from three weeks ago.
Most smartphones can send a PDF invoice from the truck. Build your template once, fill in the job details, email it before you leave the driveway. Five minutes of work that could shave a week off your average collection time.
Handling the "I'll pay you later" customer
Some customers genuinely forget. Others are slow payers. A few are trying to avoid paying altogether. Here's a follow-up system that handles all three:
- Day 0: Send invoice upon job completion.
- Day 7: Friendly text or email. "Hi [name], just a reminder that invoice #XXX for $401.63 is due. Let me know if you have any questions."
- Day 14: Phone call. Brief and direct. "Checking in on the invoice from the AC repair on [date]. Can we get that taken care of this week?"
- Day 30: Formal notice. Written letter or email stating the amount is overdue and referencing your late fee terms.
- Day 60+: Decision time. Small claims, collections agency, or write it off. Depends on the amount.
Most people pay at the day-7 reminder. They just needed a nudge. The ones who make it past day 14 without paying usually need a phone call, not another email.
Residential vs. commercial invoicing
Residential invoicing is simple. One customer, one invoice, payment at completion or within a week.
Commercial is a different animal. You'll deal with PO numbers, approval chains, Net 30 or Net 60 terms, and accounts payable departments that only process invoices on certain days. A few tips for commercial HVAC work:
- Get the PO number before you start. No PO, no payment. Don't learn this the hard way.
- Send invoices to the right person. The facility manager who called you isn't always the person who pays you. Ask: "Who should I send the invoice to?"
- Follow their format. Some commercial customers have specific invoice requirements. Ask upfront. Submitting in the wrong format delays payment by another billing cycle.
- Factor payment delays into your pricing. If a commercial customer pays Net 60, that's two months of float. Your prices should reflect the cost of waiting.
Your invoice template
If you want a ready-made HVAC invoice template along with job costing sheets and expense trackers, the free ProTradeOps toolkit has all of it in one download. Built for trade businesses, not generic freelancers.
Get paid faster with better invoices
The free ProTradeOps toolkit includes HVAC invoice templates, expense trackers, and job costing sheets.
Download free →Two things that speed up payment more than anything
Take payment on-site. A card reader on your phone costs nothing (Square, Stripe, PayPal all offer free readers). Swipe the card when the job's done. No invoice needed for residential work. You get paid immediately and the customer doesn't have to remember to write a check.
Offer a small discount for same-day payment. "2% discount if paid today" on a $1,500 install saves the customer $30 and saves you weeks of waiting. On a $1,500 job, that $30 is a bargain compared to chasing payment for a month.
The goal is simple: do good work, document it clearly, and make it as easy as possible for the customer to pay you. Everything else is just process.
Skip the template, maybe: If you are sending more than a few invoices a week, a dedicated tool saves real time. FreshBooks generates invoices, tracks payments, and sends reminders automatically. Templates are a fine starting point, but they do not chase down late payers for you.
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