The Cadastro de Pessoas Físicas (CPF; Portuguese for "Natural Persons Register") is the Brazilian individual taxpayer registry identification, a number attributed by the Brazilian Federal Revenue to both Brazilians and resident aliens who pay taxes or take part, directly or indirectly, in activities that provide revenue for any of the dozens of different types of taxes existing in Brazil. By means of this universal number the Federal Revenue computers can estimate the income tax that is due, thus directing fiscalisation.

Each individual has a number, formerly printed on a paper document or on a blue plastic credit-card-sized card. Since the 1970s the use of this number has been extended to a series of other purposes, and without a CPF it is almost impossible to lead a normal life in Brazil.

The number printed on the document is an eleven-digit figure, of which the two last numbers are the result of an arithmetic operation on the nine previous ones, so that any typing mistake will result in an invalid number. In the beginning the number used to be temporary but, as too many people used different numbers to evade tax, it is now permanent, though cancelled after some time after the person's death. To stop people from obtaining more than one registration, the registry checks for birth date, mother's name and voting registration number. Because of the permanent character of the registry, one does not actually need to have the card, but only to remember the number.

The possession of the CPF is not required, but it is a prerequisite for such procedures as opening bank accounts, getting or renewing a driver's license, buying or selling real estate, taking loans, applying for jobs, and getting a passport.

Though permanent, the validity of the CPF is not unchallenged: it will be pending after one year or cancelled by omission after two years without paying income tax or making an income tax declaration. To prevent cancellation, people who don't pay income tax formerly needed to send "exempt reports" to the Federal Revenue, but since 2008 this feature is no longer necessary.

If the CPF is pending or cancelled by omission, it still can be regularized by delivering the income tax declaration and paying it, or by paying a regularization fee in the case of people who don't need to pay income tax.

The Federal Revenue has recently issued the "e-CPF", an electronic document that can be used as a nationwide, publicly provided cryptographed signature key.