Here is the issue... Some clients prefer to pay in cash and they do not want me to charge them the sells tax. On those cases I can not use the number that BOOKs gives me, because then when I make a new invoice to a different client the tax department will know that I jump one invoice.

Even thou is not my problem, but the clients problem (under our law), I still do not want to have to respond to the tax department for that.

So again, if I make invoice number 009 (for example), and under my account I will always keep it as well, but when I send it, I will like to send it with a different format, like :  00100030002000200009

That final number is the format for our invoices here in my country. The las few numbers refer to the invoice.

What can I do?

I will like to have the option to have my internal invoice number for my own account, and the possibility to have a different number for the invoices that I send to the clients that request the tax or not.

What choices do I have?