Every NFC-e, the electronic consumer receipt Brazilian stores issue, is authorized by the tax authority of the state where the sale happened before it is printed. The slip you get at the counter (the DANFE NFC-e) is only a summary. The legal receipt is the signed XML the state holds, and you can open it from the slip's QR code or its 44-digit access key.
Open it from the QR code
Scan the QR code at the bottom of the slip with your phone's camera. It opens the consultation page of the issuing state's SEFAZ, with the store's name and CNPJ, each item with its quantity and price, the taxes, the payment method and the authorization status. No login is needed.
Type the 44-digit access key
When the QR code is damaged, type the access key (chave de acesso) printed under it on the NFC-e consultation page of the right state. The first two digits are the state's code (35 is São Paulo, 33 Rio de Janeiro, 31 Minas Gerais), which tells you which SEFAZ to use: NFC-e is a state document, so there is no single national page for it. Most state pages ask you to fill in a captcha.
Read the status
"Autorizado o uso" means the receipt is valid. "Cancelada" means the store cancelled it after printing, and a key the portal cannot find usually means the receipt was issued in contingency and has not been transmitted yet, or the key was mistyped.
Receipts with your CPF
When you give your CPF at checkout, the receipt is issued to you. States with consumer programs, such as Nota Fiscal Paulista in São Paulo, then list your receipts in your account on the program's site.
Companies: NF-e instead of NFC-e
A purchase made for a company with its CNPJ is usually documented by an NF-e (model 55), not an NFC-e. The company receives those through the national NF-e distribution service with its digital certificate, which our Portuguese guide to downloading the XML covers step by step.
Keeping NFC-e receipts
The thermal slip fades within months. Photograph it in the Smartbills app and the receipt is kept with its items, taxes and total, ready for an expense report. Receipts that reach your email, from online stores or delivery apps, are captured from the inbox without a photo.