If I bought a player for 12m over 12 months, at the end of each month I lose 1m . The other team recieves 1m every month so I assume it is the same for the user. So if another team are paying you £1m every month for a year I guess your budget will increase by £1 milloion each month
Unless like Medmax said, the board automatically do it for you right away. But if your desperate for immediate funds then try and get the money immediately.