Part-Time Workers
Part-time workers and workers hired for short periods of time are treated the same as full-time employees for federal income tax withholding and social security, Medicare, and FUTA tax purposes.
Generally, it doesn’t matter whether the part-time worker or worker hired for a short period of time has another job or has the maximum amount of social security tax withheld by another employer. See Successor employer , earlier in this section, for an exception to this rule.
Income tax withholding may be figured the same way as for full-time workers or it may be figured by the part-year employment method explained in section 6 of Pub. 15-T.