Normally, a freelancer only needs an Official Receipt. But you may also have a sales/billing invoice if you needed it.

You should not burden yourself on the confusing procedure on application for Authority to Print Receipts & Invoices.

Almost all BIR Revenue District Offices have an Accredited Printers near them. 
You may ask the BIR officers, they're happy to suggest you one.

You should hire an accredited printer that will do all the procedure required in 
printing your receipts. 

You only need to provide:
     1. Photocopy of BIR Certificate of Registration
     2. Photocopy of BIR Form 0605 - Annual Registration Fee

The average cost for 10 booklet is Php1,500.00 - Php2,500.00. 
Each booklet consist of 50pcs receipts in duplicate or triplicate
copy depending on your choice. You may only deposit a down payment 
(Usually Php500.00 for 10 booklets) and pay the balance when the
receipts are printed. The accredited printer will take one to two
weeks to finish the receipts.

You should receive the following:

1. 10 Official Receipt Booklets
2. BIR Form 1921 Authority to Print with BIR Stamp (You will need
   this ATP when you will print another receipts afterward)
3. BIR Form 1906 with BIR received stamp
4. Printer Certificate of Delivery of Receipts and/or Invoice

You may now issue an Official Receipts to your customers!

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