Invoice Number Generator

The Invoice Number Generator turns a set of formatting choices into a ready-to-use list of sequential invoice numbers, solving a chore every freelancer and small business meets at some point: how to number documents so they sort correctly, look professional, and never collide. You control five things — an optional text prefix, the starting number, how many numbers to generate, the digit padding, and a separator that can be a hyphen, slash, underscore, or nothing. A checkbox optionally prepends today's date in YYYYMMDD form, a scheme that keeps invoices naturally chronological even across restarts. The tool generates the list live, shows the first and last numbers and the total count as quick stats, and displays a pattern badge that previews the exact layout. Two guardrails keep output sane: the count is clamped to between 1 and 1,000, and padding is clamped to between 1 and 10 digits, each with an explanatory note when clamping happens. The finished list copies easily or downloads as a .txt file.

1. 1

   Type an optional Prefix such as INV, or leave the field blank.

2. 2

   Set the Starting number, Count, and Padding fields — count and padding are clamped to 1-1000 and 1-10.

3. 3

   Pick a Separator from the dropdown: Hyphen, Slash, Underscore, or None.

4. 4

   Tick the Date stamp checkbox to prepend today's date as YYYYMMDD.

5. 5

   Read the Generated, Sample first, and Sample last stats, then copy or download the full list from the result box.

• Numbering a new year's invoices with a date prefix so they sort chronologically.
• Generating sequential ticket or receipt codes for a small event.
• Producing order numbers for an online store before the sales system exists.
• Creating reference numbers for client quotes under a shared prefix.
• Resuming a sequence after a system migration by starting from the last used number plus one.
• Standardizing document IDs across departments with a fixed padding scheme.

• Pick a scheme before you start billing — changing prefixes or padding mid-year breaks the sequence's consistency.
• Always zero-pad: without padding, INV-9 sorts after INV-100 in almost every file manager.
• Note that the date stamp uses your device's local date, so check the Date badge before generating a batch that spans midnight.
• Use the clamping guards to your advantage, but watch for the amber notes so a typo of 10000 does not silently become 1000.
• Keep a record of the last number used, because the generator always starts fresh from the value you enter.
• Avoid the slash separator when the numbers will end up in filenames, where / is illegal on most systems.

• Adopt a year-based prefix such as 2026- so each January you can restart the sequence cleanly.
• Use the pattern badge to confirm the exact layout before copying or downloading a batch.
• Prefer underscores over slashes when numbers will end up in filenames.
• Generate in 1,000-number chunks for annual archives, keeping each file small enough to scan.