Required Fields on an Invoice

A valid invoice needs specific information to be legally compliant, properly processed, and paid on time. Missing fields cause payment delays, audit issues, and compliance problems. Here’s what every invoice should include.

Essential Invoice Fields

Every business invoice should contain these core elements:

1. The Word “Invoice”

The document should clearly identify itself as an invoice. This distinguishes it from quotes, estimates, purchase orders, and receipts.

2. Unique Invoice Number

A sequential identifier for tracking and reference. Requirements:

• Must be unique (never duplicated)
• Should be sequential for audit trails
• May include prefixes (INV-2024-0001)
• Required for most tax jurisdictions

3. Invoice Date

The date the invoice is issued. This often determines: - When payment terms start - Which accounting period the expense belongs to - Tax reporting period

4. Vendor/Seller Information

Complete identification of who is billing:

• Legal business name
• Business address
• Phone number
• Email address
• Tax identification number (EIN, VAT number, etc.)

5. Customer/Buyer Information

Who is being billed:

• Company name
• Billing address
• Contact name (optional but helpful)
• Customer account number (if applicable)

6. Description of Goods/Services

Clear itemization of what is being charged:

• Item descriptions
• Quantity
• Unit of measure
• Unit price
• Extended price (quantity × unit price)

7. Total Amount Due

The total the customer must pay, including:

• Subtotal
• Any taxes
• Shipping/handling
• Discounts
• Grand total

8. Payment Terms

When and how payment is expected:

• Due date or payment terms (Net 30, etc.)
• Payment methods accepted
• Early payment discounts (if offered)
• Late payment penalties (if applicable)

9. Currency

Especially important for international transactions:

• Currency code (USD, EUR, GBP)
• Clear indication on all amounts

Additional Recommended Fields

These aren’t always legally required but make processing easier:

Legal Requirements by Region

United States

No federal invoice content law, but for tax purposes include:

• Seller name and address
• Buyer name and address
• Date
• Description of goods/services
• Amount
• Tax ID (for 1099 reporting)

European Union (VAT Invoices)

EU VAT Directive requires:

• Sequential invoice number
• Invoice date
• Seller’s VAT number
• Buyer’s VAT number (B2B)
• Full names and addresses
• Description of goods/services
• Quantity
• Unit price (excluding VAT)
• VAT rate applied
• VAT amount
• Total including VAT
• Date of supply (if different from invoice date)

United Kingdom

Post-Brexit, UK follows similar VAT requirements:

• Invoice number and date
• Seller’s name, address, VAT number
• Customer’s name and address
• Description and quantity
• Unit price and total (ex. VAT)
• VAT rate and amount
• Total including VAT
• For B2B: Customer’s VAT number

Canada (GST/HST)

Required fields include:

• Supplier’s name and GST/HST number
• Date
• Total amount paid or payable
• For $150+: Buyer’s name, payment terms, description

Australia (GST)

Tax invoices must include:

• “Tax Invoice” heading
• Seller’s identity and ABN
• Date
• Description of goods/services
• GST amount (or statement that total includes GST)
• For $1,000+: Buyer’s identity

Industry-Specific Requirements

Construction

Often require: - Mechanic’s lien information - Progress billing percentages - Retention amounts - Certified payroll references (government contracts)

Healthcare

May need: - CPT/HCPCS codes - Patient information (appropriately anonymized) - Provider NPI numbers - Insurance information

Government Contracts

Additional requirements: - Contract number - DUNS/CAGE numbers - Certification statements - Progress payment applications

Best Practices for Invoice Fields

Be Specific in Descriptions

Poor: “Services rendered” Good: “Software development - Phase 2 user authentication module, 40 hours @ $150/hour”

Include All Reference Numbers

• Your invoice number
• Customer PO number
• Contract number
• Project codes
• Any reference the customer needs for processing

Clearly Show Tax

• Separate subtotal from tax
• Show tax rate applied
• Include tax registration number
• For tax-exempt: note the exemption reason

Make Payment Terms Clear

• Specific due date (not just “Net 30”)
• How you calculate due date
• Accepted payment methods
• Where to send payment

Provide Contact Information

Make it easy for AP to reach you: - Billing contact name - Phone number - Email address - Website for online payments

Common Invoice Errors

Missing or Duplicate Invoice Numbers

Creates confusion, duplicate payment risk, and audit issues.

Incorrect Addresses

Delays delivery and may cause tax compliance issues.

Vague Descriptions

Makes matching difficult, triggers review requests, delays payment.

Wrong or Missing Tax Information

Can result in non-payment, rejected invoices, or compliance penalties.

No PO Reference

If customer requires POs, missing reference causes immediate rejection.

Math Errors

Incorrect extensions or totals create exceptions and delays.

Invoice Field Checklist

Use this checklist to verify invoices:

□ Document labeled "Invoice"
□ Unique invoice number
□ Invoice date
□ Vendor name and full address
□ Vendor tax ID / registration number
□ Customer name and billing address
□ PO number (if required by customer)
□ Clear item descriptions
□ Quantities and units
□ Unit prices
□ Extended prices (correctly calculated)
□ Subtotal
□ Applicable taxes (with rates)
□ Total amount due
□ Currency
□ Payment terms / due date
□ Payment instructions
□ Contact information

Key Takeaways

• Required fields vary by jurisdiction—know your local rules
• Include PO numbers and references your customer needs
• Clear descriptions speed up approval
• Tax information is critical for compliance
• When in doubt, include more information rather than less
• Standardize your invoice format for consistency

Want vendors to submit invoices with all the fields you need? See how BillerPlus creates a structured submission process →