What to include on an invoice: a complete guide for small businesses

Published Friday 15 May 2026

Table of contents

• What is an invoice?
• What to include on an invoice
• How to format invoice numbers
• Invoice payment terms explained
• Invoicing tips for different industries
• Common invoice mistakes to avoid
• Invoice requirements by state
• What an invoice should include for cross-state business
• Invoice tools and automation for compliance
• Invoice with confidence using Xero
• FAQs on invoice requirements

Key takeaways

• A standard invoice should include 10 essential elements: your business name and contact details, client information, a unique invoice number, invoice and due dates, itemized line items with descriptions, payment terms, tax information, total amount due, accepted payment methods, and any relevant notes.
• Invoicing requirements vary by state. Differences typically involve how sales tax, trade names, and license numbers appear on invoices, along with late fee limits and industry-specific rules.
• For cross-state sales, apply the destination or service location tax rules, show tax separately, and confirm you're meeting invoicing requirements in both your state and the buyer's state.

What is an invoice?

An invoice is a formal document that records a transaction between a business and its customer. It includes an itemized list of goods or services provided, costs, fees, and sales taxes, along with details about both the seller and the buyer.

Vendor invoices serve as a seller's request for payment. They function like bills but also act as a record of the transaction for tax and bookkeeping purposes.

What to include on an invoice

An invoice should include 10 essential elements: your business details, client information, a unique invoice number, dates, itemized line items, payment terms, tax information, total amount due, payment methods, and additional notes. Including each of these helps you get paid faster and keeps your records organized for tax time.

Your business name and contact information

Every invoice should start with your legal business name, address, phone number, and email. If you operate under a trade name (also known as a "doing business as" or DBA name), include both your legal name and your registered trade name.

Many states require you to register a fictitious business name before using it on invoices or other business documents. Check your state's requirements to make sure you're in compliance.

Client name and contact details

Include your client's full name or business name, along with their billing address and email. Accurate client details help prevent payment delays caused by invoices being sent to the wrong person or department.

If your client has provided a purchase order (PO) number or account number, include that as well. This makes it easier for their accounts payable team to match and process your invoice.

Unique invoice number

Every invoice needs a unique invoice number to help both you and your client track payments and keep records organized. A consistent numbering system makes it simpler to follow up on unpaid invoices and locate specific transactions during audits.

You can use sequential numbers (INV-001, INV-002), date-based formats (2026-05-001), or client-based prefixes (ACME-001). The format matters less than using it consistently.

Invoice date and due date

Include the date you're issuing the invoice and the date payment is due. The invoice date establishes when the transaction was recorded, while the due date sets clear expectations for your client.

Specifying both dates helps you track aging invoices and follow up promptly when payments are overdue.

Itemized line items and descriptions

List each product or service on a separate line with a clear description, quantity, unit price, and line total. Specific descriptions help your client understand exactly what they're paying for and reduce the chance of disputes.

For example, instead of writing "consulting services," write "brand strategy workshop, 3 hours at $150/hr." Vague descriptions are one of the most common reasons invoices get questioned or delayed.

If you're billing for partial work or a deposit, note that clearly. For instance: "50% deposit for website redesign project, phase one."

Payment terms

Spell out when and how you expect to be paid. Common payment terms include Net 30 (due within 30 days), Net 60 (due within 60 days), and due on receipt. If you charge late fees or offer early payment discounts, state those terms on the invoice as well.

Clear payment terms reduce confusion and give you a basis for following up on overdue invoices.

Tax information

If sales tax applies to your transaction, show it as a separate line item on the invoice. Include the tax rate, the taxable amount, and the total tax charged. If an invoice doesn't list sales tax separately, it may not serve as proof that you collected tax from the customer.

Depending on your state, you may also need to display your sales tax permit number or employer identification number (EIN). Check your state's requirements.

Total amount due

Clearly display the total amount due, including all line items, taxes, fees, and any discounts. This should be easy to find on the invoice so your client knows exactly what to pay.

Accepted payment methods

List the payment methods you accept, such as bank transfer, credit card, check, or online payment. Including payment details like your bank account number or a payment link removes friction and helps your client pay faster.

Additional notes

Use the notes section for any extra context, such as a thank-you message, a reference to a contract or agreement, or special instructions. You can also include your return or refund policy here if it's relevant to the transaction.

Keep records of all invoices in case of customer disputes or tax audits. The IRS provides tips on recordkeeping, and Publication 583 covers recordkeeping requirements in detail.

How to format invoice numbers

An invoice number is a unique identifier assigned to each invoice you send. It helps you track payments, organize records, and quickly locate specific transactions. A good numbering system is consistent, easy to understand, and scalable as your business grows.

Here are common invoice numbering formats that work well for small businesses:

• Sequential numbering: start at 001 and count up (INV-001, INV-002, INV-003). This is the simplest approach and works well for businesses with a single client base.
• Date-based numbering: include the year or month in the number (2026-001, 202605-001). This makes it easy to sort invoices by time period.
• Client-based prefixes: add a short client code before the number (ACME-001, SMITH-015). This is helpful if you want to quickly see all invoices for a specific client.
• Project-based numbering: include a project code (PROJ-A-001, WEB-003). This works well for agencies or consultants managing multiple projects at once.

Whichever format you choose, avoid starting your numbering at 1, as it can make a new business look inexperienced. Starting at 100 or 1000 is a common practice. Also avoid reusing invoice numbers, even for different clients, as duplicate numbers create confusion during audits.

Invoice payment terms explained

Payment terms define when you expect to receive payment and any incentives or penalties tied to the timing. Setting clear invoice payment terms on every invoice helps you manage cash flow and reduces the chance of late payments.

Here are some of the most common payment terms you'll see on invoices:

• Due on receipt: payment is expected as soon as the client receives the invoice. This is common for one-time services or small transactions.
• Net 15: payment is due within 15 days of the invoice date. This works well for ongoing client relationships where you need faster turnover.
• Net 30: payment is due within 30 days. This is the most widely used payment term for business-to-business (B2B) transactions.
• 2/10 Net 30: the client receives a 2% discount if they pay within 10 days; otherwise, the full amount is due in 30 days. Early payment discounts can improve your cash flow.

If you plan to charge late fees, include the penalty terms on the invoice. For example: "A 1.5% monthly late fee applies to invoices unpaid after 30 days." Check your state's laws, as some states cap the interest rate or require specific disclosure language for late fees.

Invoicing tips for different industries

Different industries have different invoicing needs. Tailoring your invoices to your specific field helps you look professional, get paid faster, and stay compliant with industry norms.

Consulting and professional services

A freelance or consulting invoice should include a detailed breakdown of hours worked, your hourly or project rate, and a clear description of the services delivered. If you're billing by milestone, specify which deliverables are covered by each line item.

Include the project name or engagement reference so your client can easily match the invoice to the work. For retainer-based arrangements, note the retainer period and any hours or services that exceeded the retainer scope.

Construction and trades

Construction invoices often involve progress billing, where you invoice for completed stages of a project. Break down costs by labor, materials, equipment, and any subcontractor fees. Include the project address and relevant permit or license numbers.

Many states have specific invoicing requirements for contractors, especially for government projects. Always check your state's rules for construction invoicing.

Retail and e-commerce

Retail invoices should include product names, SKU numbers or item codes, quantities, unit prices, and applicable sales tax. If you're selling across state lines, apply the correct destination-based sales tax rate for the buyer's location. Here's how to calculate sales tax for your business.

For returns or exchanges, issue a credit memo that references the original invoice number. This keeps your records clean and makes reconciliation straightforward.

Freelance and creative work

Freelance invoices should clearly describe the scope of work completed, such as "logo design, three revision rounds" or "blog article, 1,500 words." Include usage rights or licensing terms if they're part of your agreement.

If you require a deposit before starting work, issue a separate invoice for the deposit and note the remaining balance on the final invoice. A freelance invoice template can help you get started. This protects both you and your client.

Common invoice mistakes to avoid

Small invoicing errors can lead to delayed payments, disputes, and compliance issues. Avoiding these common mistakes helps you get paid on time and maintain professional relationships with your clients.

• Missing or incorrect client details: sending an invoice to the wrong contact or misspelling a company name can delay processing. Double-check the client's billing name, address, and any PO numbers before sending.
• Vague line item descriptions: descriptions like "services rendered" or "miscellaneous" invite questions. Be specific about what you delivered, the quantity, and the rate.
• Forgetting to include payment terms: if your invoice doesn't state when payment is due, your client has no deadline. Always include a clear due date and your preferred payment methods.
• Not showing tax separately: lumping tax into the total without a separate line item can create problems during audits. Show the tax rate, taxable amount, and tax total as their own line.
• Using duplicate invoice numbers: reusing numbers, even across different clients, causes confusion in your records and during tax audits. Use a consistent, unique numbering system.
• Sending invoices late: the longer you wait to send an invoice after completing work, the longer it takes to get paid. Send invoices promptly, ideally on the same day you deliver the goods or services.
• Not following up on overdue invoices: if a payment is past due, a polite follow-up reminder can resolve the issue quickly. Learn more about how to reduce late payments and keep cash flow steady.

Invoice requirements by state

The United States doesn't have federal invoicing laws, so invoice requirements are determined by state and local regulations. Most states don't have overarching invoice rules, but other state laws may affect what you include on an invoice, especially around sales tax, trade names, and industry-specific requirements.

You generally can't use a fictitious business name on an invoice unless that name is registered with your state. Beyond that, here's what you need to know for some of the most business-active states.

California

California doesn't have statewide invoice compliance requirements, but several codes apply to specific industries:

• Sales of liquor (except beer) between licensees must be documented on an invoice that includes the purchaser's name and address, the date of sale, an invoice number, and details about the liquor. These invoices must be available for examination and kept separate from non-alcoholic product invoices.
• Repair services, including appliance repair, auto repair, and electronics repair, must include details about the item being repaired, where it was repaired, and an itemized breakdown of all parts and services.
• Government contractors have additional formatting and submission requirements for invoices related to public contracts.

Even if your industry doesn't have specific rules, always note the sales tax collected on the invoice. Without it, the invoice can't serve as proof that you collected sales tax from the customer.

New York

New York has specific rules about how contractors should invoice government entities, including prompt payment laws that require government agencies to process invoices within a set timeframe.

If you provide an invoice to a consumer in New York, it must include:

• all items or services being provided
• the cost
• the date of the purchase or service
• the delivery date
• your business details
• a phone number for your billing or customer service department

If the invoice contains automatic renewal terms, those must be clearly disclosed. Receipts issued at the time of purchase only need to include your name, address, and phone number.

Texas

Most of Texas's invoicing laws apply to government contractors. The state's prompt payment laws require most government entities to pay contractor invoices within 31 days of receiving them.

While Texas doesn't have general invoicing requirements for most transactions, merchants involved in door-to-door or home solicitation sales must provide a receipt or contract that includes:

• the same language as the oral contract
• the date of the transaction
• the name and address of the merchant
• a statement explaining that the buyer may cancel the transaction before midnight of the third business day after the transaction

This three-day cancellation right applies specifically to door-to-door and home solicitation sales under Chapter 601 of the Texas Business and Commerce Code. It doesn't apply to all merchant transactions.

Florida

Florida has statutes governing how contractors should invoice government agencies, along with industry-specific laws for businesses that deal with tobacco products or fire suppression equipment.

Under Florida law, you may not issue an invoice for goods or services that haven't been ordered unless you include the following warning in 30-point bold face type:

This is a solicitation for the order of goods or services, and you are under no obligation to make payment unless you accept the offer contained herein.

There are stiff penalties for not following this law, so make sure your solicitation invoices include the required disclosure.

Illinois

Illinois has special laws for government contractor invoices, which must detail subcontractor services and meet specific formatting and submission requirements. The state's prompt payment rules require state agencies to pay contractor invoices within 60 days or face interest charges.

Illinois also has industry-specific rules:

• If you buy tobacco for resale from out of state, you must keep the invoice available for inspection.
• If you own a car dealership and advertise prices based on the dealer's invoice, you must let customers inspect the invoice on request.

Washington

Washington state requires businesses to collect and remit sales tax, and invoices should clearly show the tax amount charged. The state uses destination-based sourcing, meaning you apply the sales tax rate for the buyer's location, not yours.

Contractors working on public projects have additional invoicing requirements, including detailed breakdowns of labor, materials, and applicable retainage amounts.

Massachusetts

Massachusetts requires businesses to collect a 6.25% sales tax on most tangible goods and certain services. Your invoices should show this tax as a separate line item. The state also requires home improvement contractors to provide detailed written contracts before starting work over a certain dollar threshold.

If you sell motor vehicles, Massachusetts has specific documentation requirements that include the vehicle identification number (VIN) and odometer reading on the invoice.

Georgia

Georgia requires businesses to collect state and local sales tax, and invoices should display the combined rate for the buyer's jurisdiction. The state uses a destination-based sourcing model for sales tax.

Georgia also has specific rules for motor vehicle dealers and auto repair shops, which must provide itemized invoices that break down parts, labor, and any applicable fees.

The IRS maintains links to state government websites where you can find detailed information about your state's requirements.

What an invoice should include for cross-state business

If you're sending an invoice to a customer in another state, you need to meet the invoicing requirements in your state and the buyer's state. Cross-state transactions add sales tax complexity, so it's important to get the details right.

Here's what to keep in mind for cross-state invoicing:

• Apply destination-based sales tax: in most cases, sales tax applies at the buyer's location, not yours. Check the state or local jurisdiction to find the correct rate.
• Understand nexus rules: selling, shipping, or providing services in another state may create nexus, which means you're required to collect and remit sales tax there. Some states trigger nexus based on a dollar threshold (for example, $100,000 in sales), while others use a transaction count.
• Show tax as a separate line item: when billing across state lines, always display the sales tax separately on the invoice. This is important for compliance and helps both you and your client during audits.
• Register for sales tax accounts: if you've established nexus in another state, you may need to register for a sales tax permit in that state before collecting tax.
• Keep detailed records: cross-state transactions are more likely to be reviewed during an audit. Maintain clear records of the buyer's location, the tax rate applied, and any exemptions claimed.

Invoice tools and automation for compliance

Invoice automation software can help you stay compliant without spending hours on manual data entry and tax calculations. The right tool handles the repetitive parts of invoicing so you can focus on running your business.

Here's what to look for in invoicing and automation tools:

• Automatic tax calculation by jurisdiction: the software should apply the correct sales tax rate based on your client's location, reducing the risk of errors on cross-state invoices.
• Customizable templates with required fields: pre-built templates that include all essential invoice elements help you stay consistent and avoid missing information.
• Digital record retention: cloud-based storage makes it easy to keep invoices organized and accessible, meeting the IRS's recordkeeping requirements without filing cabinets.
• Multi-state tax management: if you sell across state lines, look for software that tracks nexus thresholds and applies the right rates automatically.
• Automated payment reminders: sending follow-up reminders for overdue invoices improves cash flow without adding to your workload.
• Online payment options: letting clients pay directly from the invoice speeds up the payment cycle.

Compared to manual invoicing, automation reduces errors, saves time, and gives you a clear audit trail. For businesses operating in multiple states, automated tax calculation is especially valuable.

Invoice with confidence using Xero

Creating a professional invoice is straightforward when you have the right accounting software. Xero makes it simple to generate and send invoices that include all the essential elements. It automatically calculates sales tax across multiple jurisdictions, supports online payments, sends payment reminders, and creates audit-ready records so you can stay compliant with state requirements.

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FAQs on invoice requirements

Here are answers to frequently asked questions about invoice requirements, compliance, and best practices for small businesses.

What is legally required on an invoice in the US?

The United States doesn't have federal invoicing laws, so requirements depend on your state and industry. However, you should keep invoices with your other business tax records for at least three years in case of an audit. The IRS recommends keeping employment tax records for four years and some records for up to seven years.

Which state's rules should my invoice follow?

Your invoices must comply with the laws in the state where you operate. If you're shipping goods or providing services to a customer in another state, you may also need to meet that state's requirements, especially around sales tax collection and disclosure.

Do I need to include my EIN or sales tax permit number on my invoices?

It depends on your state. Some states require you to display your EIN, your sales tax permit number, or both. Check your state's regulations to confirm what's needed.

Are electronic invoices acceptable?

For IRS recordkeeping purposes, electronic invoices are treated the same as paper invoices. Check your state's laws to confirm that electronic invoices meet any industry-specific requirements that apply to your business.

What is an invoice number and how should I format it?

An invoice number is a unique identifier assigned to each invoice. If you're switching numbering systems mid-business, start the new format at a number higher than your last invoice to avoid duplicates. Most accounting software lets you set a custom starting number and prefix, so you can migrate without losing continuity in your records.

How do I automate professional invoices for clients?

Invoicing software like Xero lets you create customizable templates, set up recurring invoices, automate payment reminders, and calculate sales tax automatically. Automation reduces manual errors and helps you get paid faster, especially if you're managing clients across multiple states.