Explain how that works.
If I earn £300 this weekend cash in hand and don't declare it, how is that a shortfall, and why does it have to be made up from the "ordinary tax-paying worker" paying more? Where is the loss?
Contrast with some migrant claiming a cash benefit which means money is actually given to him and so then can't be spent on anything else because its gone from the pot. Is that a shortfall?
I'll break it down to something simple for you .... What you are effectively saying is that I have just lost £120 million because I did not win the lottery. Which is nonsense, as I never had it in the first place.
But what is an example of a loss, is the £5 I put into some vagrants Costa cup to support his lifestyle. That money is gone and can't be spent on anything else - a loss. I had it, and then it's gone.
And just to help your understanding further, the Government (like anyone else that deals with budgets and incomes and outgoings) plans their future budgets on known and expected incomes. They collect what is owned and chase what is not paid. They don't plan budgets on some unknown future tax revenue. So if some business evades paying some tax, if that tax was not expected, it's not a loss and does not impact on revenue, and is not a shortfall that needs to be made up by the "ordinary tax-paying worker".