if you don't respond your withholding will be based as if you filed as single with 0 exemptions. see the following from the IRS. you must justify why you're entitled to the exemptions claimed. A pro likely won't be able to help unless you can justify the reason in which case you probably can save the fees by contacting the IRS yourself.
if you post your reason in this forum we MAY be able to give you our opinion but it's just that.
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We can tell your employer to withhold federal income tax at an increased rate. We do this by issuing a "lock-in letter." At that point, your employer must disregard any Form W-4 that decreases the amount of your withholding. You'll receive a copy of the lock-in letter, and we'll give you some time before the lock-in rate is effective to submit a new Form W-4. This form must include a statement that explains why you believe you're entitled to a different withholding rate or number of withholding allowances. You should send your Form W-4 and supporting documents to the IRS address as shown on this webpage. Once we issue a lock-in letter, you won't be able to decrease your withholding unless we approve it.
What if I don't want to submit a Form W-4 to my employer?
Your employer must withhold income tax from your wages as if you're single with zero allowances.
How to get help
Call toll free 855-839-2235 weekdays between 8 a.m. and 5 p.m.
Fax your documents to 855-202-8300 using either a fax machine or online fax service. Protect yourself when sending digital data by understanding the fax service’s privacy and security policies.
Write to:
Internal Revenue Service
Compliance Services
Withholding Compliance Unit
310 Lowell Street, Stop 837
Andover, MA 01810
