And by increasing your deductions it will decease your income and you may not be getting as many credits as before. Also after you reduce your income to zero there is no more refund to get back but you still may owe for other things like self employment tax or the 10% early withdrawal penalty from 401k or IRA accounts.
If you have the Desktop program you can switch to Forms Mode and open Schedule A to see. If it doesn't show Schedule A in the list on the left, Then click Open Forms box in the top of the column on the left. Open the US listing of forms.
