The subventio generalis (or "general aid"), also known as collecta, was a direct tax in the medieval Kingdom of Sicily.
The subventio generalis had its origins in the obligation of the holders of fiefs in the Kingdom of Sicily to provide military service to the monarchs.
[1][2] They were required to serve in the royal army without compensation for maximum 90 days for each 20 ounces of their annual income.
[3] Most barons and counts preferred to pay the fee which thus developed into a tax already under the Norman kings of Sicily.
[1] The Holy Roman Emperor, Frederick II, who was also king of Sicily, summoned the host in each year after 1231.