There is often confusion between the CIE, RNE and CPF.
The CIE is the Foreigners ID card and the RNE is a Foreigners registration number.
You receive your RNE number when you receive your visa, the number also appears on your CIE card.
When the Federal Police stamp your passport with your visa, they will also give you a Protocol (this is equivalent to a temporary ID card) this will have your RNE number and and can be used as proof of ID.
It can take several months between getting your visa and receiving your CIE cards.
The RNE only expires in certain circumstances, for example, if the individual leaves Brazil for a period of 2 years, the CIE is valid for 10 years and then has to be renewed.
The CPF number (Cadastro de Pessoa Fisica) is the Individual Taxpayer’s Number and is required for many everyday transactions in Brazil, including opening a bank account, applying for a job, subscribing to a mobile phone company and when buying a car or property.