Help for changing WHMCS invoice enumeration

[Inversed]

Hello, we are looking for a way to reset the invoice number since we created a new company and the invoices should contain the new company information but since there is a change in the bulgarian law for invoices our first invoice has to start with number: 0000000001 (9 zeros and 1).
I contacted WHMCS about this and here's their reply:  

 

Quote

Thanks for getting in touch with WHMCS.

To reset and deliver invoices to clients that start from "1", you should leverage the Custom Invoice Numbering Format feature: https://docs.whmcs.com/Tax_Configuration#Custom_Invoice_Numbering_Format

You can set the "Next Invoice Number" value to "1". It is possible to set a custom invoice number format. However, that would not allow you to automatically set a prefix of variable length based on the invoice number (so adding 9 zeros for invoices 1-9, then 8 zeros from invoice 10-99, etc.).

You could potentially use the InvoiceCreation hook point to execute custom code to add a new custom invoice number (with leading zeros) via the UpdateInvoice API command:

• https://developers.whmcs.com/hooks-reference/invoices-and-quotes/#invoicecreation
• https://developers.whmcs.com/api-reference/updateinvoice/

I trust that gives you a good starting point for your customisations/development. For further assistance customising WHMCS I’d recommend posting on our Developer Corner community where our friendly and knowledgeable community will I’m sure be pleased to assist in this matter: https://whmcs.community/community/41-developer-corner/ .

Regrettably we are unable to assist with customisations/development here as part of product technical support.

Has anyone developed this or created something similar ? Can you guys help ?