Employer Stopped Withholding Taxes Mid Year Without Notifying Employees. Is This Legal?

I’ve been with my previous employer for about 2 years and after the first year I stopped checking my paystubs since payroll was always correct (I know, big mistake????) . About 5 months before I resigned, they stopped withholding taxes from our checks without notifying anyone. I’m relatively new to the country and not quite familiar with the tax law, so I apologize if this is a stupid question, but Is that legal for an employer to do? My W4 is filled out correctly and nothing has changed since I got hired so just wondering if this is something common I should look out for in the future.

For reference, I reside in Florida. Single, no dependents.