For example, if your birthday is October 9th, 1984, it will be written as 09/10/1984. Date of Birth, Date of Birth Format, Income Tax Return We have supplied the right format for entering the date of birth when completing the return. You must enter your date of birth correctly or an error message will appear when you try to file your return. If you were born after December 31st, 1959, you cannot use a computer to file your tax return. An IRS employee must process your return at a location that has access to electronic filing systems. These locations are called "service centers". There are over 100 service centers across the country. They are located in post offices, some banks and others private businesses that have been approved by the IRS to provide tax services. An IRS employee will be able to assist you with any questions regarding your return. It is very important to give your correct date of birth when you file your tax return. If your date of birth is incorrect, the IRS will not be able to calculate your correct income tax liability because it does not know how much additional tax should be withheld from your paycheck. They will assume that you are not subject to any additional taxes based on your age. This could cause you to get a notice from your employer requiring you to submit evidence of your eligibility to work beyond your normal retirement age before your benefits can be continued.