Receita Federal http://www.receita.fazenda.gov.br/ Secretariat of Federal Revenue. Includes full text of the Brazilian National Revenue and Taxation Code. [Portuguese] Brazilian source
Paying Taxes in Brazil http://www.doingbusiness.org/ExploreTopics/ PayingTaxes/Details.aspx?economyid=28 World Bank. This page is a table showing the taxes and mandatory contributions that a medium-size company must pay or withhold in a given year in Brazil, as well as measures of administrative burden in paying taxes. [English, French, Portuguese, Spanish]
