Invoices are sequentially numbered in Chargebee starting from "1". 

You can also customize the numbers formats for the invoices and credit notes.

Here are the various elements you can customize in the invoice number:

1. Prefix

• An alpha-numeric prefix can be added at the beginning of the invoice number that will appear on all the invoices.

2. Dynamic Prefix

• You can include the date, month or year that would automatically be updated in the invoice numbers. This would be useful if you’d like to reset the invoice number sequence at the beginning of every month or year.

3. Separators 

• You may choose to use the hyphen (-) as a separator between the prefix and the numeric parts.

4. Numeric part

• You can set your invoice numbers to begin from a specific number, say 50001. However, you need to ensure that this number doesn’t already exist in the system(when a dynamic prefix doesn’t exist).

• You can also set a fixed number of digits for an invoice number such as 6 digits. So the number will be preceded by 0s for a lower digit number, for example,  000010 > … > 012345 >... > 123456

Note:

1. Although random invoice numbering is not strictly supported, Chargebee can help by allowing you to increment your invoice numbers by a value greater than 1.

2. You need to ensure that the invoice number sequence that you set does not conflict with an existing number in your Chargebee account. 

Related articles and documentation:

Invoice and credit note numbering

How to customize invoices in Chargebee