Employer's federal quarterly employment taxes are reported on:

Form 941 is used to report quarterly employment taxes(including federal income tax, Social Security, and Medicare).

Form 940 reports FUTA taxes (A), not quarterly employment taxes.

Form 944 is for small employerswho file annually instead of quarterly.

Form 945 is for non-wage income withholding (D).

References:

IRS Form 941 Instructions