The receipt for your ticket is the credential itself, because it was purchased without the convenience fee or any other service charge and the Municipal Decree n.º 50.896/2009, article 39 states:
DECREE No. 50.896, OF OCTOBER 1st, 2009 (DOC of 10/02/2009), approves the Regulation of the Tax on Services of Any Nature - ISS.
Art. 37 - The passes, tickets or entrance vouchers used by the taxpayers to allow the public access to the event's venue, including the free ones, which must be issued by the providers of public entertainment services, are considered tax documents for the purposes of the Municipality's tax legislation, and may only be sold or distributed if previously authorized by the City's Finance Department.
If you need other proof besides the ticket itself, you can request a receipt for your order, just contact us by e-mail email@example.com.