My husbands employer did not withhold federal or state taxes this check? How can this affect us?

Question

This is the only time it has happened.

Answer 1

Nothing bad will happen to you.  Keep track of the withholding and if you are coming up short, increase the withholding to avoid underpayment penalties.

If you are really worried, you can send in an estimated tax payment equal to the withholding that wasn't taken out.  

When an employer messes up like this, it is important to keep all paystubs and reconcile the withholding with the W-2.

Answer 2

Why not?

It will just be less money withheld to cover the taxes you may or may not owe later.