Box 4. Federal Income Tax Withheld
Enter backup withholding. For example, if a recipient does not
furnish its TIN to you in the manner required, you must backup
withhold on payments required to be reported in box 1 (which
may be reduced by the amount reported in box 2), box 3, and
box 8 on this form.
first contact the institution to find out the reason. if you failed to provide an ID # ask for instructions. if they say they were informed by the iRS you'll have to contact it for the reason