CNPJ is the Tax ID of the legal entity to which you export your goods
CPF is the Tax ID of the individual to which you export your goods
It is mandatory to inform the CNPJ number of CPF number on the Comercial Invoice you will join with the goods you send to Brazil. A lack of CNPJ or CPF prevents the release of the consignment, resulting in its return to the origin.
So if you sell goods to Brazil, you need to ask form CPF or CNPJ n° to your customer at checkout.