> ## Documentation Index
> Fetch the complete documentation index at: https://documentation.claruswms.com/llms.txt
> Use this file to discover all available pages before exploring further.

# How Invoice Numbers Work

> Understand how invoice numbers are generated automatically and how to customise them with your own numbering scheme or prefix.

## Customising Invoice Numbers

Invoice numbers are automatically generated in sequence. However, you can easily customise these numbers, which is particularly useful if you are migrating from another invoicing system.

<Steps>
  <Step title="Use pre-populated invoice numbers">
    When you create a new invoice, the system will automatically suggest the next available invoice number in sequence. You can simply use this default number.
  </Step>

  <Step title="Change the invoice number">
    If you want to use a different number, type your desired number into the **Invoice Number** field. After you save, this new number will become the starting point for all future sequential invoices.

    <Warning>After saving, the new number becomes the starting point for future sequential invoices. Make sure this is intentional.</Warning>
  </Step>

  <Step title="Add a prefix">
    To add a prefix such as "Inv-" or "Invoice-", type it directly into the **Invoice Number** field before the actual number.
  </Step>

  <Step title="Ensure no duplicate numbers">
    The system will not allow you to use an invoice number that is already in use. Each invoice must have a unique identifier.

    <Warning>The system rejects duplicate invoice numbers. If you try to use an existing number, you will be prompted to choose a different one.</Warning>
  </Step>
</Steps>

<Tip>You can include letters, numbers, and other characters in your invoice numbers for maximum flexibility.</Tip>