The Chancellor was also supposed to ensure the legality of monarch's actions, especially whether or not they could be considered illegal in the context of pacta conventa (an early set of documents containing important laws, in some aspects resembling today's constitutions).

A 16th-century Polish lawyer, Jakub Przybylski, described the Chancellor as the king's hand, eye and ear, translator of his thoughts and will.

The Vice-Chancellor was, however, not a subordinate of the Chancellor and his independence was specifically confirmed by the laws passed during the reign of king Alexander Jagiellon.

From 1507, Sigismund I the Old decided that the title of Grand Chancellor of the Crown would be rotated between secular and ecclesiastic nobles, and at least one Chancellor (both in the Grand and Deputy pair and in the Crown and Lithuanian one after the Union of Lublin) was required to be a secular person.

From the 15th and 16th centuries, after the reforms of Alexander, Sigismund I and the Union of Lublin, the power and importance of the Chancellor's office was stabilised, as a senatorial office lesser than that of the hetmans (military commanders who had, however, no right to vote in the Senate) and the Grand Marshals, but more important than that of the Grand Treasurers, Court Marshal and others.

By custom, the Grand Chancellor of the Crown directed the Commonwealth foreign policies towards the west – Western Europe and south – Ottoman Empire, while the Grand Chancellor of Lithuania the policies towards the east – Muscovy (later, the Russian Empire).

2 secretaries (one responsible for private correspondence, the second for official) presented prepared letters to the king for his signature.

No copies were made, but were instead entered in the archives – books called Metrics (Polish: Metryki), who were taken care of by the two metricans (2 in Poland and 2 in Lithuania respectively).

The Chancellery staff had no wages, just like the Chancellors, but in the middle of each reception room was the box into which all clients were supposed to deposit a varying amount of money, and nobody who planned on coming back could afford to be mean.

Many enlightened chancellors did not restrict the positions in their staff to nobility (szlachta), and often sponsored intelligent applicants from other social classes, not only by hiring them to the chancellery but by paying for their studies at universities in Poland and abroad.

The nobles (the szlachta) who controlled the Senate were usually unwilling to increase taxes and levied upon them, which meant that Poland very rarely declared wars on its own.

The army was undermanned and under equipped (since usually any suggestion of bigger military budget when enemy was not on the doorstep was labeled as warmongering) and lands of Rzeczpospolita were constantly ravaged by new invasions, crippling its economy.