One of the best-known functions of the Parliament is its legislative one, that is, passing laws. Catalan laws are proclaimed by the President of the Generalitat in the name of the King of Spain and are published in the Diari Oficial de la Generalitat de Catalunya (official journal of the Generalitat of Catalonia) and the Boletín Oficial del Estado (official gazette of Spain).

As bills, budgets have a specific function for two reasons: because they are passed annually and above all, because each year they serve to renew the contract of trust between the Government and its Parliamentary majority, and to give the opposition the chance to criticise the Government and put forward its own proposals.

The Parliament of Catalonia may legislate on those matters defined in the Statute of Autonomy, in accordance with the Constitution as exclusive powers of the Generalitat, as well as on shared powers, within the framework set by the State as principles or as lowest common legislative denominators.