Subcontractor Invoice Guide: Billing a General Contractor

When you work as a subcontractor, your customer isn't the homeowner. It's a general contractor (GC) with its own paperwork rules, approval process, and payment schedule. An invoice that would be fine for a homeowner can sit in a GC's accounts payable queue for weeks if it's missing a PO number, a lien waiver, or the right billing period.

This guide covers how to invoice as a subcontractor, what GCs usually require, how retainage and pay-when-paid clauses affect you, and the tax forms that come with the relationship. If you're the GC hiring subs, the same checklist tells you what to ask for.

What makes subcontractor invoicing different

• Your contract is with the GC, not the owner. Your invoice must match the subcontract and its billing terms.
• GCs bill the owner on a cycle. Many collect sub invoices by a cutoff date each month so they can include them in their own pay application.
• Retainage is common. The GC may hold back a percentage of each payment until the project is complete.
• Lien waivers are usually required with each invoice or payment.
• Tax paperwork: the GC will usually ask for a Form W-9 before paying you.

What to include on a subcontractor invoice

• Your business name, address, phone, email, and license number
• GC's name and billing contact, plus any vendor or subcontractor number they assigned you
• Project name and address
• Subcontract number and PO number, if any
• Invoice number, date, billing period, and due date
• Scope or schedule of values for your trade, with percent complete
• Approved change orders with their numbers (see How to Write a Change Order)
• Retainage held this period and to date
• Previous billings and payments
• Amount due this invoice
• Lien waiver enclosed (usually conditional; see What Is a Lien Waiver?)
• Payment terms as stated in the subcontract

Before your first invoice: get the requirements

Ask the GC's project manager or accounting contact:

1. What's the billing cutoff date each month?
2. Do you need a specific pay application format (such as AIA G702/G703 or the GC's own form)?
3. What lien waiver forms do you use, and when?
4. What's the retainage percentage, and when is it released?
5. Do you need certificates of insurance, certified payroll, or other documents with each invoice?
6. Who should invoices be sent to, and how?

Getting these answers once saves a rejected invoice every month.

Pay-when-paid and pay-if-paid clauses

Many subcontracts include a clause tying your payment to the GC getting paid by the owner:

• Pay-when-paid usually sets the timing: the GC pays you within a set time after it's paid.
• Pay-if-paid tries to make the owner's payment a condition of your payment, shifting the risk of owner non-payment to you.

States treat these clauses very differently. Some limit or don't enforce pay-if-paid clauses, and many have prompt-payment laws that set how quickly GCs must pay subs once they've been paid. Read the clause before signing.

This article is general information, not legal or tax advice. Talk to an attorney about subcontract terms and to a tax professional about your tax situation.

Monthly sub invoices follow the same pattern every time. SnipInvoice can draft yours from a quick spoken update ("Demo Ave project, 55% complete on rough-in, change order 2 done") and flags any number it's unsure about instead of guessing. You review it and share the PDF from your own phone by email, text, or WhatsApp. See how it works.

Taxes: W-9 and Form 1099-NEC

Form W-9. The GC will typically ask you for a W-9 with your legal name, business name, and taxpayer identification number before paying you. See About Form W-9.

Form 1099-NEC. Businesses that pay a nonemployee (including many subcontractors) for services must generally file Form 1099-NEC when payments for the year reach the reporting threshold. The IRS says the threshold is $600 for payments made before 2026 and $2,000 for payments made in 2026, with inflation adjustments after that. Payments to corporations are generally exempt, with some exceptions. See About Form 1099-NEC and the IRS page Am I required to file a Form 1099?

Contractor or employee? Calling someone a "sub" doesn't make them one. The IRS looks at behavioral control, financial control, and the relationship. See Independent contractor (self-employed) or employee?

Example subcontractor invoice

All names, numbers, and prices below are fictional examples, not pricing guidance.

Example Plumbing Subcontractors (fictional) · 41 Sample Ave, Anytown, USA · License #EXAMPLE-PS00
Bill to: Example General Contracting (fictional), Attn: Project Accounting · Vendor #: V-2210
Project: Example Office Build-Out, 1200 Demo Ave · Subcontract #: SC-077 · PO #: EX-4410
Invoice #: 2026-052 · Period: May 1 to May 31 · Date: May 25 (GC cutoff) · Terms: per subcontract

Schedule of values (example)	Value	% complete	Completed to date
Underground plumbing	$9,000.00	100%	$9,000.00
Rough-in	$14,000.00	70%	$9,800.00
Fixtures and trim	$8,000.00	0%	$0.00
Change Order #2: add break room sink (approved May 8)	$1,600.00	100%	$1,600.00
Totals	$32,600.00		$20,400.00

Summary	Amount (example)
Completed to date	$20,400.00
Less retainage, 10%	−$2,040.00
Less previous billings (net)	−$8,100.00
Amount due this invoice	$10,260.00
Retainage held to date	$2,040.00

Enclosed: conditional progress lien waiver for $10,260.00; current certificate of insurance on file.

Example only.

If you're the GC: what to collect from subs

• A signed subcontract with scope, price, and billing terms
• A W-9 before the first payment
• Certificates of insurance (and keep them current)
• Invoices by your cutoff, in your format
• Conditional waivers with each invoice; unconditional waivers after payment
• Records of every payment for your 1099 filing and your books. See Invoice Numbering and Record Keeping.

Then roll your subs' billing into your own invoice to the owner. Our Remodeling Invoice Guide and Progress Billing for Contractors show how.

Common subcontractor invoice mistakes

• Missing the GC's cutoff date. Your invoice slides to next month's cycle.
• No PO or subcontract number. Accounts payable can't match it.
• Billing unapproved changes. Wait for the signed change order.
• Forgetting retainage math. Show it every time so the totals reconcile.
• Signing unconditional waivers early. Wait for cleared funds.
• Skipping your trade details. Electrical and HVAC subs should still itemize clearly; see our electrician and HVAC guides.

FAQ

How do I invoice a general contractor as a subcontractor?

Follow the subcontract's billing terms: invoice by the GC's cutoff, in their format, showing schedule of values, percent complete, change orders, retainage, previous billings, and amount due, with any required lien waiver.

Do subcontractors need to fill out a W-9?

GCs usually request one before paying you so they can report payments on Form 1099-NEC if required.

What is the 1099-NEC threshold?

Per the IRS, $600 for payments made before 2026 and $2,000 for payments made in 2026, with inflation adjustments after that. Check the IRS site for current rules.

What is retainage on a subcontractor invoice?

A percentage the GC holds back from each payment until the project or your scope is complete. See Retainage in Construction.

What does pay-when-paid mean?

A clause that ties the timing of your payment to when the GC is paid by the owner. Enforceability varies by state.

When should a subcontractor send an invoice?

By the GC's monthly billing cutoff, or as the subcontract specifies.

Bill the way your GC needs it

The best subcontractor invoices match the subcontract, hit the cutoff, and come with the right paperwork. Do that every month and your payments move with the GC's cycle instead of falling behind it. To turn a quick progress update into a ready-to-send invoice, try SnipInvoice. Quotes are free, and the Unlimited plan is $19.99 a month.