This type of offence, set out in Articles 318 - 322 of the Criminal Code, is based on an agreement between a public official and a private individual in which the first accepts a form of compensation which is not due to him in exchange for performing some act in the exercise of his duties.
There are two forms of corruption:  the first involves the public official acting outside his authority or failing to perform his duty, while the second  involves him acting within his authority.

Both forms of corruption can be: 
antecedent: when recompense is agreed in anticipation of the action and with the aim of inducing it.
subsequent: when the recompense is given after the action takes place.

Law 86/90 unified the two situations, leaving the form of the offence unchanged.

Source: Ministry of Interior - Department of Public Security

Source: Ministry of Justice