This question isn't clear. Did you never compute Social Security and Medicare on your payroll for paid time off?

Vacation pay is the same as any other job wage pay and subject to the same taxes. Especially for salary people. You're paying them for being an employee, but you also give them time off. Paid time off or not, doesn't matter, because Salaried are paid, by definition, even if on a day off.

You might have a situation where you track by hours or pay for job worked under occupation codes, to bifurcate worker comp. And short/long term leave might fall under a third-party pay.

But regular payroll to employees is subject to these payroll taxes, as are "supplemental" or one time wages including bonus pay, standby pay, shift differential, overtime, holiday pay, vacation pay.