Economic crime

The government gave me a task today. Let's just call it an espionage mission.
A rather hard one...therefore, I seek help.

Before I begin, I need to explain some things first.
The government has a sub-department that deals with the technologies (support, delivery, hardware etc). This is where the hardcore programming guys are, with an IT-director on top. Let's call it IT-department.

Basically, we give them money, and they provide us with the systems.
Lately, they've been recruiting a lot of people and my boss is wondering where they're getting the money from. Because he know the amount of money he has given them for this period is not going to cover all the new recruits.
So now he's suspicious and wants to know if the IT-director is really listening up all the income and outcome on the State Budget.


My job is to somehow find out where they get their money from without letting them know it. Asking the person who's responsibility for the economy for the IT-department is useless, since he's siding with them.

I don't know much about economic crime (not sure if I'm using the right term), this is the first time I'm doing this and I'm clueless. My boss wants me to give him suggestions on how to find out their budget without blowing the "cover" or whatever that I'm doing.
The goverment is of course giving me all the access I need.
I feel like Solid Snake or Sam Fisher.

Any suggestions?
All I can come up for now is that they have found a company that gives them hardware that are cheaper than the company that is listed up in the contract.

Jam it back in, in the dark.