Need Help - "invoice" Vs "tax Invoice"

[Zen]

1) I noticed that most companies that sell products or service to me, they normally send an "INVOICE" (or "BILLING NOTE") first. After I pay them, then they'll issue me a "TAX INVOICE / RECEIPT". Sometimes the the "INVOICE" and "TAX INVOICE / RECEIPT" have the same serial number, but sometimes it's a different serial number.

Is there any difference from my method - I issue "TAX INVOICE" immediately to the customer when I deliver my goods to them, and when they pay, I issue a "TAX INVOICE COPY / RECEIPT". Both my "TAX INVOICE" and "TAX INVOICE COPY / RECEIPT" have the same serial number.

2) If I deliver goods to a customer on Consignment, what are the documents normally issued? For example, if I deliver 10pieces to a customer on consignment, should I issue a "DELIVERY NOTE" for these 10pieces and if he sells 5 pieces then I issue him a "TAX INVOICE" for the 5 pieces?

[ludosiam]

As far as I know the company issuing a tax invoice is liable to pay tax for the amount stated even if the recipient doesn't pay. Therefore tax invoices are issued only after payment has been received.