What is an invoice number generator?

It creates a sequence of unique invoice numbers based on a prefix and starting number, then logs each one with the date, client, and any notes you add. Each number is unique and ready to paste into your invoices or accounting software.

Why do invoice numbers need to be sequential?

Many tax authorities require invoice numbers to be unique and sequential without gaps. Sequential numbering also makes audits and reconciliation much easier.

What happens when I change the prefix?

The tracker computes the next available number separately for each prefix. Your existing entries are preserved, so you can keep separate sequences for different entities or years.

Yes, but only in your browser's localStorage. Nothing is uploaded to any server. Clearing browser data removes the saved state.

What is a good invoice numbering format?

A common format is PREFIX-YEAR-SEQUENCE, like INV-2026-0042. Use a 4- or 5-digit sequence with leading zeros for consistent sorting. Include the year so you can safely restart the sequence annually without confusing old invoices.

Can I have gaps in my invoice numbering?

Depends on your jurisdiction. Some countries (Germany, Italy) require gapless sequential numbering for tax compliance. Others allow gaps if documented. If you void an invoice, most accountants recommend keeping the number and marking it as void rather than reusing it.

Invoice Number Generator

Generate sequential invoice numbers with a prefix, starting number and leading-zero padding. Attach client names and PO references to each number and keep a local log so you never reuse the same number twice. Everything is stored in your browser.

How to use

Set a prefix

Enter a prefix like INV-2026- or leave it blank.

Set the starting number

Choose where the sequence begins.

Choose leading zeros

Pad numbers to a fixed width for consistent formatting.

Generate the next number

Click Generate Next Number — the tracker saves it with date, client and notes.

Prefix

Starting Number

Leading zeros

Next available

INV-1001

Generated Numbers (0)

Stored in this browser

No numbers generated yet. Click Generate Next Number to start.

All data is stored only in your browser. Nothing is uploaded to any server.

Features

Sequential numbering

Auto-increments without gaps, per prefix.

Separate sequences per prefix

Keep different sequences for different entities or years.

Client and PO log

Attach client names and PO references to each number.

Local storage persistence

Your log is saved in your browser — nothing is uploaded.

Reset with confirmation

Clear the whole log in one action with a confirmation dialog.

Common use cases

Maintain a sequential invoice numbering system
Track which invoice numbers have been used
Log client names against each invoice number
Keep a separate sequence per business entity

Frequently Asked Questions

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