Fonte:
http://www.portaldasfinancas.gov.pt/pt/external/sire/downloadSIRE.action
http://info.portaldasfinancas.gov.pt/NR/rdonlyres/8740ACFC-6E7C-4652-86C0-ED790C3CA18C/0/Circular%2011%20-%20Tabela%20PRATICA%20ART_68%20CIRS.pdf
