How many times a year can you file tax exempt with your employer? Can your employer tell you no you can not do that?

If you claim to be exempt from withholding you have to resubmit a new W4 each year.

The IRS has the right to review your W4. If they determine that your W4 claims too many exemption allowances, or incorrectly claims to be tax exempt, they can require your employer to withhold a minimum amount of tax. You should review the requirements for claiming that you are exempt from witholding - see:

www.irs.gov/pub/irs-pdf/p505.pdf

You can do it as many times as you want, provided you can show EACH TIME that you hade NO tax liability the previous year.