The Papacy in the Late Middle Ages
Papal Government
Camera Apostolica
The camera apostolica was the financial arm of the Church. Its treasurer was the head of the administration, but the chamberlain made financial policy. The chamberlain was effectively the papal prime minister, for he controlled the papal mint and most administrative officials reported to him. He was the judge in legal disputes concerning papal revenues and he supervised the tax collectors.
The camera apostolica (the phrase means "apostolic office" and is often simply called the Chamber) was also the office that responded to petitions, so it was the site of much activity. Petitioners who could afford it hired proctors, who were a bit like professional lobbyists, to see their petition through the maze of offices and officials.
As you would expect, the Chamber was primarily responsible for collecting revenues. The most important of these were the servitia, annates, and the fructus intercalares. The first two were similar in nature. They were a one-time payment made by a new office-holder, for any office over which the pope had control The most lucrative were the cardinal hats, which could generate a large chunk of cash, which helps explain why popes kept creating more cardinals.
Even more important were the many bishops, archibishops, abbots, and lesser positions. Here the popes systematically tried to claim more and more offices as being under their authority. It was not that the popes were trying to control who became Bishop of Wherever, it was simply that if the office were under papal provision, as the phrase went, then they got the income of the annate or service. Under John XXII, this was fixed as being the first year's income. Few had that kind of cash, so typically they borrowed the money. If the bishop died two years later, then the papacy got a new payment when the new bishop entered office.
Remember that this was the age of the Black Death. Plenty of bishops died. This was, in fact, one way the popes were able to extend their authority, for in some places so many clergy died that they appealed to the pope to choose a successor. He did, but he thereby claimed right of provision. John XXII declared that any see whose holder happened to die while at the curia was reserved to the papacy. In 1363, Urban V reserved all sees across Europe whose incomes were above a certain level.
The fructus intercalares were the fruits (income) of the period during which there was no bishop or abbot actually in office. The bishopric obviously didn't stop producing income after a bishop died, so who got the income? It didn't go in a bank account! Rather, it went to the papal treasury.
This could represent a substantial amount of money for a great archbishopric. Here again, the Black Death actually worked to bring in money, though often conditions were so bad that collection proved all but impossible. And here again, there was room for abuse. Popes were accused of deliberately delaying the choice of a new bishop in order to enjoy the revenues. This might or might not have been the case, but once the perception was out there, it was impossible to dispel.
The Chamber collected other monies as well. Various monarchs owed monies or had granted subsidies. Donations were made. Income from sale of indulgences, from jubilees, and so on, all were handled through the Chamber. The popes had vassals, most notably the Kingdom of Sicily, and had revenues there. By the law of ius spolii, the property of clergymen who died intestate reverted to the papacy.
The papacy also sold "expectancies": a hopeful candidate would pay for the right to be considered for provision to benefices when they became vacant. Many of the charges of simony stemmed from this practice. It was not technically the selling of a church office, but it could sure amount to the same thing, when the highest bidder on the list is the man who got the office.
The papal treasury was, as you can imagine, a large and busy place. Clement VI established a system of regional tax collectors, which served to make an unpleasant and worldly side of the papacy even more visible to the public.
There was also a camera secreta, that served as the pope's own treasury. We don't know much about it because no records were kept.