Benedict XIV, who bought Palazzo Madama in 1755, made it the seat of his government. The new function of the building required important renovation work. A second courtyard was opened, in the place which houses today the Senate chamber, and the square in front of the façade was redesigned by Luigi Hostini. In later years the building was to serve various other uses: courts of law, police headquarters and tax office. Some rooms were even turned into prison cells. In 1798-99 the building became the central office of the Roman Republic.
In 1850 Pius IX (Giovanni Mastai Ferretti, 1846-1878) transferred the Ministry of Finance and Public Debt and the pontifical postal administration to Palazzo Madama and carried out additional alterations.