How to number invoices. Set it up once, never think about it again.
Good invoice numbers are unique, in order and easy to quote on a payment. Choose a format once and let the app count up for you.
- ✓ Free PDF download
- ✓ No signup
- ✓ Your logo
- ✓ Auto-saved on this device
- ✓ Nothing uploaded
Private by design
Your invoice is built in your browser. Client names, prices and bank details never touch a server.
Looks professional
Clean layout with your logo and brand color, real selectable text, automatic page breaks for long invoices.
Picks up where you left off
Your details are saved on this device, so the next invoice takes seconds. Clear it any time.
How to number your invoices with SiskinBill
- Choose a format (see the table below) and type your first number in Invoice number. A new draft starts at INV-0001.
- Fill in the invoice and download the PDF as usual.
- For the next one, click Start a new invoice. The last number in the invoice number goes up by one (INV-0007 becomes INV-0008, 2026-041 becomes 2026-042). Your business details, logo, currency, paper size, notes and terms stay; the client and lines are cleared.
- Keep every PDF you send. SiskinBill keeps only the current draft in this browser, not a history of past invoices, so your saved PDFs (or a simple spreadsheet log) are your record.
Numbering formats that work
| Format | Example | Good for |
|---|---|---|
| Plain sequence | INV-0001, INV-0002 | Most small businesses |
| Year and sequence | 2026-001, 2026-002 | Seeing at a glance which tax year an invoice belongs to |
| Client code and sequence | ACME-001, ACME-002 | A few large repeat clients, where your local rules allow separate series |
Rules of thumb
- Never reuse a number, even for an invoice you cancelled. In many countries invoice numbers must be unique and follow one or more continuous series, so keep a note of any number you void.
- Fixing a mistake: issue a corrected invoice with a new number and mention the old number in Notes. Some countries require a formal credit note instead, which SiskinBill doesn't produce, so check with your accountant.
- Leave room: four digits (0001) last for 9,999 invoices and keep numbers sorting correctly in folders and spreadsheets.
- New year: with a year prefix, change it by hand in January (2027-001). Start a new invoice only counts up the last number.
- Starting number: you don't have to start at 1. Starting at 1001 is common, as long as you count up from there.
Invoice generator FAQ
Can invoice numbers contain letters?
Yes. Prefixes such as INV- or a year are fine. What matters is that every number is used once and that they follow a clear order.
What should I do if I skipped an invoice number?
Don't reuse or renumber anything already sent. Note the skipped number and why in your records, so the gap can be explained later.
Does SiskinBill remember which numbers I've used?
Only the current draft is saved in this browser. Start a new invoice counts up from it, but there's no list of past invoices, so keep your PDFs or a short log.
Is this invoice generator really free?
Yes. Create and download as many PDF invoices as you like, with no signup. Each PDF carries a small "Made with SiskinBill" line in the footer.
Is my data uploaded anywhere?
No. Everything happens in your browser, and your draft is stored only in this browser's local storage. Use "Start a new invoice" to clear it. The only things ever sent are cookie-free visit counts (Cloudflare Web Analytics, see Privacy), anonymous counts of which buttons are used (for example, 'a PDF was downloaded'), and an anonymous error report if something breaks (error text, browser, page, app version). Never anything you type or upload. Button counts are skipped if your browser sends Do Not Track or Global Privacy Control.
How is tax calculated?
Tax is applied to the subtotal after the discount. Each line is rounded to the cent, and the tax is rounded once. Shipping is added after tax.
Can I add my logo?
Yes. Upload a PNG or JPG. It is resized in your browser and placed at the top of the PDF.
Which currencies are supported?
USD, EUR, GBP, CAD, AUD, NZD, CHF, JPY, INR and MXN. Where the PDF font has no symbol (for example the rupee sign), the currency code is used instead.
Is this tax or legal advice?
No. Check what your invoices must include where you do business (for example a VAT or GST number).