How to number an invoice.

What is an invoice number?

It is the reference you assign to an invoice, such as INV-2026-001. The same reference helps connect the PDF, the email you send, a client's question, and your record of any payment. It can contain letters as well as digits; it does not have to describe the whole project.

Keep it separate from the client's purchase-order number, a quote reference, and a payment transaction reference. Those identify different records. If your client gives you a PO number, put that in Junocity's Project reference field while keeping your own invoice number in Invoice number.

Three invoice-number formats to consider

For a small manual workflow, one shared sequence is easier to check than several client or project counters. Leading zeros keep references visually consistent. Use short, neutral prefixes rather than private client information.

These are organizational examples, not a universal legal numbering standard. Follow any invoice-series or correction rules that apply to your business. A format that is convenient for filing does not by itself establish tax compliance.

Keep a small invoice register

Before issuing a new invoice, look up the last number you used. A spreadsheet or your existing accounting system can hold the reference, issue date, client, amount and currency, due date, and location of the saved PDF. Keep payment status based on your own payment records.

If more than one person issues invoices, agree who allocates numbers or use a shared system that controls the sequence. Two people opening a blank editor cannot see which numbers the other person has already used.

Download a simple invoice register

Use the blank CSV to start a record in your spreadsheet app. The separate example shows three fictional invoices in one shared sequence, including a repeat client and a partial payment.

• Download the blank invoice register (CSV) — column headings only, ready for your first entry.
• Download the fictional worked register (CSV) — three illustrative rows. The clients, amounts, payment status and PDF filenames are examples.

The register has columns for the invoice number, issue date, client, currency, total, due date, client PO or project reference, payment status, PDF filename and notes. Dates use YYYY-MM-DD; amounts use a decimal point and a separate currency column.

Use the register alongside the editor

1. Open the blank CSV. If your spreadsheet app asks how to import it, choose comma-separated columns. Keep invoice references as text so any leading zeros remain intact.
2. Check your next number. Search the whole invoice-number column before assigning a reference. The example progresses from INV-2026-014 to INV-2026-016 across two clients.
3. Record the issued document. After reviewing and saving your invoice PDF, add its details on one row. Replace the example filename with the actual name or location you use. The CSV does not contain or create a PDF.
4. Update from your own payment records. Enter payment status manually. For a partial payment, note the verified date, amount and remaining balance while keeping the original invoice total unchanged. See the invoice and receipt guide.
5. Save your updated file. Keep your register and invoice PDFs in your own recordkeeping system. Sort the entire table together so a client's details stay with the right invoice.

These CSV files contain no formulas or automatic tracking. They do not allocate numbers, detect duplicates, calculate balances or check payments. Changes are made in your spreadsheet app; Junocity does not receive or save the register. Keep different currencies separate when reviewing amounts.

Set the number in Junocity

1. Open the invoice generator and find The details.
2. Replace the starting value INV-001 with the reference checked against your register.
3. Check the preview, then download the PDF and record the issued reference in your own system.
4. Use that same reference in the invoice email and any later reminder.

Junocity does not save invoice history, increment numbers, reserve a reference, or check for duplicates. A fresh or reset editor starts with INV-001 again. Downloading a PDF does not advance a counter.

Copies, corrections, and missed numbers

If a client asks for another copy of the same invoice, resend the existing checked document with its original reference. Creating a new invoice number for an unchanged copy can make one bill look like two.

If the amount, client, or other issued details are wrong, keep a record of the original and follow the correction process appropriate to your business. A corrected invoice, cancellation, or credit note can require different handling. Junocity does not manage those records or issue credit notes for you.

If your sequence has a gap, investigate it in your register. Do not silently renumber invoices already sent just to make the list look tidy. Record what happened and check any applicable requirements before changing an issued record.

Check before sending

• The number identifies this invoice and has not already been used for a different one.
• The invoice PDF and accompanying email show the same reference.
• Client PO and project references are in the appropriate separate field.
• Your register contains the reference and the downloaded document.