Is what the company deducts monthly under the heading of zakat sufficient on behalf of the employee?

Zakat on wealth is not obligatory unless it reaches the nisab (minimum threshold) and a full hawl (lunar year) has passed on it. If the company deducts an amount as Zakat with your permission and knowledge, then that suffices for you, and the company acts as your agent. However, if the deduction is made without your permission, it is not sufficient, because Zakat is not valid unless there is an intention when it is disbursed.