when to redetermine withholding
a new form w 4 must be filed with a taxpayer s employer whenever the taxpayer s personal or financial situation changes e g they get married have a baby or their spouse enters or leaves the workplace the new withholding goes into effect no later than the first payroll period ending 30 days after giving the revised form to the employer 6 the employer may implement it sooner but isn t required to do so it s also possible to request that a specific dollar amount be withheld in addition to other tax withholdings this may be helpful for taxpayers receiving a year end bonus or for those who simply want to boost withholding near the end of the year perhaps to cover taxes on investment income such as capital gain distributions made at the end of the year individuals can also request that an additional amount be withheld with form w 4 be sure to file a new form w 4 if your personal or financial situation changes if you don t you could end up having too little money withheld throughout the year which would affect what you must pay come tax time 