Invoicing in the US is relatively straightforward compared to many other countries — there's no federal invoicing law that applies to all businesses. But that doesn't mean anything goes. Get the basics wrong and you could face delayed payments, tax headaches, or disputes that are hard to resolve. Here's what you actually need to know.
Is there a legal invoicing standard in the US?
No single federal law dictates exactly what must appear on every invoice. However, a few things shape what's expected:
IRS requirements apply if you're claiming business expenses or need to document income
State sales tax laws vary by state and determine whether you must charge and remit tax
Contract law governs payment disputes — your invoice is part of the paper trail
In practice, a professional invoice that includes the right information protects you legally and makes it easier to get paid.
What every US invoice should include
Your business information
Your full legal name or business name
Your address
Your email or phone number
Your EIN (Employer Identification Number) if you have one — required if you're incorporated or have employees. Sole proprietors can use their SSN, but an EIN is safer.
Client information
Client's full name or business name
Their billing address
Invoice details
A unique invoice number
Invoice date
Payment due date
Itemized services or products
Clear description of each item or service
Quantity and unit price
Subtotal
Taxes
Sales tax if applicable (see below)
Total amount due
Payment terms and methods
Accepted payment methods
Any late fee policy
Sales tax: the most misunderstood part
Sales tax in the US is state-level, not federal. Whether you need to charge it depends on:
What you're selling — Physical products are almost always taxable. Services are taxable in some states, not others. Software and digital products fall into a grey area that varies by state.
Where your client is located (economic nexus) — Since the 2018 South Dakota v. Wayfair Supreme Court ruling, states can require you to collect sales tax even if you don't have a physical presence there, as long as you exceed their sales threshold (typically $100,000 in sales or 200 transactions per year in that state).
Where you're based — If you only work with clients in your own state, you generally only need to worry about your state's rules.
If you're a freelancer selling services domestically, you likely don't need to charge sales tax in most states. But if you're selling physical goods or SaaS products, consult a tax professional.
Late fees: are they enforceable?
Yes — but only if they're stated upfront. You can't add a late fee after the fact. If you want to charge interest on overdue invoices, include it in your invoice terms:
"Invoices unpaid after 30 days are subject to a 1.5% monthly interest charge."
Most states allow late fees as long as they're disclosed and not usurious (excessively high). 1–2% per month is generally safe.
1099 forms and when they apply
If you're a freelancer or independent contractor, your clients may be required to send you a Form 1099-NEC at the end of the year if they paid you $600 or more. This is their responsibility, not yours — but keeping clear invoice records makes it easier to reconcile.
Likewise, if you pay other contractors more than $600 in a year, you may need to issue 1099s to them. Keep your invoices organized year-round so tax season isn't a scramble.
Contracts vs invoices: what's the difference?
An invoice is a request for payment — it's not a contract. Your contract (or statement of work) is what defines the scope, timeline, and terms of the engagement. Your invoice references that agreement and triggers the payment.
Both matter. If a client disputes a payment, you'll want both the signed contract and the invoice as evidence. An invoice alone, without an underlying agreement, is harder to enforce.
Keeping records
The IRS recommends keeping business records for at least 3 years from the date you filed the return they relate to — longer if you underreported income. In practice, most accountants recommend 7 years to be safe.
This means storing copies of every invoice you send, whether paid or unpaid. A good invoicing tool does this automatically.
The simplest way to stay compliant
You don't need a lawyer to invoice correctly in the US — you just need a consistent system. Clervo handles the structure for you: unique invoice numbers, itemized line items, due dates, and a clean paper trail for every transaction. Free to use, no monthly fee.
This article is for informational purposes only and does not constitute legal or tax advice. Consult a qualified professional for guidance specific to your situation.
Last updated: May 2026