A tax increase reduces income, and thus, aggregate expenditure. If the tax increase is assumed to be a lump sum tax the aggregate expenditure will move downward in a parallel fashion. A tax increase may be warranted in the case of excessive demand causing inflation. In the leakage-injection analysis the tax increase is a leakage and is added to saving.
In the late 1960's, a tax surcharge was enacted in the United States. Its purpose was to decrease the amount going to aggregate expenditure, i.e. create a negative multiplier effect, because the economy was experiencing an increasing inflation.