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Invoice numbers: What they are and how to manage them for your business.

Learn how invoice numbers help track payments, organise records, and keep your business finances running smoothly.

Explore Adobe Acrobat for business

A woman’s hand filling out a paper invoice.

An invoice number is a unique identifier assigned to every invoice your business issues. It acts as a reference point for you, your clients, and your accounting system, ensuring every transaction is accurately recorded and easily traceable.

Each invoice number is exclusive to a particular bill and helps distinguish it from others. Whether you use invoicing software to auto-generate numbers or create them manually, having a clear numbering system simplifies financial management.

How to create an invoice number?

There’s no universal rule for generating invoice numbers, but a consistent approach will make your system easier to manage. Here are some common methods businesses use:

  • Sequential numbering: Start from “0001” and increase with each new invoice.
  • Date-based system: Combine the invoice date with a sequence, e.g., “20240201-001” for the first invoice on 1 February 2024.
  • Client-specific codes: Assign unique prefixes to different clients, e.g., “LM-001” for Live Marketing’s first invoice.
  • Project-based codes: Create invoice numbers linked to specific projects, e.g., “ProjA-002.”
  • Whichever approach you choose, ensure it’s easy to follow and grows with your business. Avoid repeating numbers or using generic codes, as this can cause confusion later.

Why invoice numbers are important?

Invoice numbers do more than just label a document – they offer several business-critical benefits:

  • Track payments: Easily match payments to the right invoice and detect any overdue accounts.
  • Resolve disputes: Quickly locate and cross-check specific invoices if questions or conflicts arise.
  • Simplify taxes: Provide clear records for tax filings and audits, reducing errors and saving time.
  • Organise financial records: Create a clear, chronological paper trail for income tracking and bookkeeping.
  • Help your clients: Invoice numbers allow customers to align payments with their own records, avoiding miscommunication.

A hand holding a magnifying glass over a medical bill, focusing on the fine print and numbers.

Streamline your invoicing with Adobe Acrobat.

Digital tools can simplify your invoicing process, reducing errors and speeding up payments. With Adobe Acrobat, you can:

  • Create custom invoice templates.
  • Add invoice numbers automatically.
  • Collect e-signatures securely.
  • Save and organise invoices as PDFs.
  • Take control of your invoicing and keep your business running smoothly with Adobe Acrobat for Business.

Frequently asked questions

What’s the difference between an invoice number and a PO number?

A purchase order (PO) number tracks an order before goods or services are delivered. An invoice number is issued afterward to request payment.

Can I reuse an invoice number?

No, each invoice number must be unique. Reusing numbers can cause confusion and disrupt your records.

Should proforma invoices have invoice numbers?

Proforma invoices generally don’t need invoice numbers as they’re estimates, not payment requests. If you number them, ensure they don’t interfere with your regular sequence.

More resources

Content as a Service v3 - Thursday 3 April 2025 at 15:18

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