When in career mode loan in any player to your team.

Once the transaction is completed go to the budget allocation screen and set the ratio 0:100, so you have no transfer budget and lots of player wages remaining.

Then end the contract with the loaned player. When you return to the budget allocation screen the ratio will be 99:1 and you will have over £2,100,000,000, however this stays at that amount until the ration is set to 50:50 so I recommend setting it to this to achieve highest wage and budget.

You can also follow the same cheat but instead of loaning in a player you can release one or recall a player you've loaned out (teams like Man U already have players loaned out).