No, almost certainly it's not. I'm going to guess that the stock sold was received through some Employer Stock Incentive program like a NQSO, RSU, etc. In these situations the cash for the stock sold "for taxes" is passed back to the employer, who pays the governments(s) and then sprinkles the taxes throughout your W-2. Ask your payroll department if you are unsure.
If a broker actually withholds - called "backup withholding - then that withholding must be reported on Form 1099-B.
Tom Young
