[mikeash]

It's specifically a cost of labor. The business spends $X on you as an employee, and you receive $Y. The difference between X and Y is tax. The fact that some of the difference is technically removed before the money is transferred to you, and some of it is technically removed after the money is transferred, makes no difference in the end.

[hussong]

In Germany, the employer's contribution to social security is tax-free for the employee and is a fully deductible cost for the employer.

Other benefits (company car, apartment, fuel etc.) are subject to employee's income tax beyond a certain threshold.

Edit: Taking a step back, there is simply a fundamental difference between taxes and payments to social security / different insurances.

[mikeash]

Taxes are tax deductible? True, but pointless.

I think the "fundamental difference" is key. I don't ultimately see any real difference between taking 12.4% of my pay (under $118,500) for Social Security, and taking a variable percentage of my pay for government operations in general. It's money, based on a percentage of what I earn, that goes to the government, i.e. an income tax.