According to Noticias ao Minuto, the rule applies regardless of the age of your pet and, in the event of non-compliance, the fine has a "minimum amount of €50 and a maximum of up to €44,890.
The law also states that "dogs born before 1 July 2008, which by virtue of Decree-Law no. 313/2003 must be marked and registered in the SIAC [Companion Animal Information System] within 12 months after the entry into force of this decree-law".
Already "cats and ferrets that were born before the entry into force of this decree-law must be chipped and registered with the SIAC within 36 months [term which ends today] after the entry into force of this decree-law".
To place an identification microchip, the animal's guardian must go to a veterinary care centre or a municipal veterinarian.