Chasing unpaid invoices in HVAC and field service businesses

Field service businesses often send many small invoices to customers with many sites, many approvers and a strict matching process. Each of those is a place an invoice can stop.

The common blockers:

• No PO or work order number. Many commercial customers will not pay an invoice they cannot match to an order. Emergency jobs are the usual gap: the technician was sent at night, and nobody raised the PO.
• Over the not-to-exceed limit. Facilities managers often issue work orders with a not-to-exceed (NTE) amount. If the repair cost more and the extra was approved by a phone call on site, the invoice can sit until someone approves it on paper.
• No proof the work was done. The approver was not on site. Without a signed job sheet, photos or a technician's notes, they cannot confirm the work and will not release payment.
• Wrong contact or address. The invoice went to the store manager who called you out, not the regional office or the AP mailbox that pays.
• Customer portals. Some facilities management companies only accept invoices uploaded to their own portal, with their reference attached. An emailed invoice can be ignored entirely.
• Disputes over hours or parts. Two technicians where the customer expected one, a part billed at a price nobody quoted, or a return visit the customer thinks should be free.

Your accounts receivable aging report will usually show the pattern. Many small past due invoices from one customer usually point to a process problem, not a cash one.

Most chasing problems can be solved at booking. For every commercial job, confirm these before the technician is dispatched:

• The PO or work order number, and whether the customer needs it on the invoice.
• The NTE limit, if there is one, and who can approve going over it.
• The billing contact or AP mailbox, which is often different from the person who called you.
• Whether invoices must go through a portal, and the customer's account or site reference.
• Your payment terms, in writing. Our guide to Net 30 payment terms covers how to set them so they hold.

For new commercial accounts, a short setup email saves weeks later:

Subject: Billing details for [Customer name] service work

Hi [First name],

Thanks for choosing us for [Site or service]. Before our first visit,
could you confirm a few billing details so our invoices reach the
right place and get paid on time?

- Where should invoices be sent? (email address or portal)
- Do you need a PO or work order number on each invoice?
- Is there a not-to-exceed limit per job, and who approves extra work?
- Who should we contact with billing questions?

Our terms are [Payment terms], as set out in [Quote or agreement].

Thanks,
[Your name]

The person who approves your invoice was usually not at the job. Give them what they need to say yes without asking you.

• A signed job sheet. Name, date and signature of whoever was on site, with the work done and time on site.
• Photos. Before and after, plus the nameplate or part replaced.
• Written approval for overages. If the job will exceed the NTE, get the approval by email or in the work order system before doing the extra work. A verbal yes on site is a common source of field service disputes.

Every day between finishing the job and sending the invoice is a day added to your wait. Send it the day the work is done, with:

• The PO or work order number, exactly as the customer wrote it.
• The site address and the customer's site reference.
• What was done, with labor and parts on separate lines.
• The signed job sheet and photos attached.
• The due date written out, not just the term.
• How to pay, and a named contact for questions.

If the customer uses a portal, upload it there, even if you also email it.

Commercial field service customers tend to pay in weekly or monthly payment runs. A sensible schedule follows that rhythm:

For the wording at each stage, see our payment reminder email templates and past due invoice email templates. The templates below cover the replies that are specific to field service.

When the PO or work order number is missing

Subject: PO needed for invoice [Invoice number], [Site address]

Hi [First name],

Our invoice [Invoice number] for [Amount] covers the [Job type] at
[Site address] on [Job date]. [It was an emergency call, so we did
not receive a PO at the time.]

Could you raise a PO or send us the work order number? We will
reissue the invoice with it straight away. The signed job sheet
is attached.

Thanks,
[Your name]

When the job went over the not-to-exceed limit

Subject: Approval for [Overage amount] on work order [Work order number]

Hi [First name],

Work order [Work order number] at [Site address] had a not-to-exceed
limit of [NTE amount]. The repair came to [Invoice total] because
[Plain reason, e.g. the compressor needed replacing, not repairing].

[Name] approved the extra on site on [Date]. The photos and job
sheet are attached. Could you confirm approval in writing so your
team can release the invoice?

If you would rather, we can split it: invoice [NTE amount] now and
the balance once the extra is approved.

Thanks,
[Your name]

Splitting the invoice gets the undisputed part paid while the rest is settled. If the customer disagrees with the extra work itself, treat it as an invoice dispute and agree what was approved before you chase further.

When the invoice went to the wrong person

Subject: Invoice [Invoice number] for [Site address]

Hi [AP contact name],

[Site contact name] at [Site address] asked us to send this to you.
Invoice [Invoice number] for [Amount] was due on [Due date]. The
invoice and signed job sheet are attached.

Could you confirm it is in your next payment run, and let me know
the best address for future invoices from us?

Thanks,
[Your name]

Planned maintenance contracts tend to be easier to collect than one-off repairs, if you bill them right. Invoice the contract in advance, monthly or quarterly, rather than after each visit. The customer approves one recurring amount once, and you stop chasing many small invoices.

For larger installs and replacements, ask for a deposit to cover equipment, and invoice the rest at agreed stages, as our guide to progress billing explains. No single unpaid amount gets large, and the customer's approval process starts earlier. If a customer cannot pay a large balance at once, a written payment plan agreement gets you a schedule instead of a vague promise.

If you are a subcontractor on a construction project, the payment terms in your subcontract matter more than anything here. Construction work can carry its own payment rules, which differ by country and, in the US, by state. Check them with a lawyer early on those jobs, not after the money is late.

A credit hold means you stop non-emergency work for a customer until overdue invoices are paid or a payment date is agreed. It is a business decision, and it works best as a rule you set in advance rather than a reaction.

Write it down: for example, no new non-emergency work once an invoice is 45 days past due without an agreed payment date. Put it in your terms. Then apply it the same way to every account, and tell the customer before it takes effect, not on the morning a technician is turned away.

Decide in advance what counts as an emergency, so the rule never leaves a building without heating or cooling over one invoice.