overwithhold

verb (used with object), o·ver·with·held, o·ver·with·hold·ing.

1. to withhold too much.
2. to deduct (an amount in withholding tax) in excess of the tax to be paid.

verb (used without object), o·ver·with·held, o·ver·with·hold·ing.

3. to withhold oneself excessively.
4. to deduct too much withholding tax.