I just wanted to add that there is another control in the system, which is the level of appropriation that is granted by the Parliament for a given year. Parliament makes money available, but it also sets an appropriation limit that takes account of funding that a government entity might derive from other sources, such as, for example, charging for its services and things like that.
When that funding level is reached, a minister has to come to the finance minister to seek the finance minister's agreement to running what's called an “operating loss”. The finance minister has to agree to any expenditure over and above the cap that Parliament has set.