Let's see how we can change the sequence number for Invoice
Please follow the path, Settings > Invoice Customization
You will see following options:
1) Daily reset sequence Number: If the transaction volume for invoices is high, the daily reset sequence is helpful. The by default prefix to the number will be the date for transaction.
2) Manual Numbering: In this option, you can enter your own numbering manually. Kindly ensure that the numbering is unique for each invoice.
3) INV Prefix followed by sequence number: This is the most preferred way of invoice numbering. The sequence number will be generated by system in progressive manner.
4) Custom Prefix & Suffix: With this option you can add Prefix of your own choice.
Indian users are required to follow GST rules for Invoice numbering. The 4th option number system is complying with GST rules in India.
You can also read How you can choose and customise Invoice Templates.