My full-time employer put )about) half my income into 'tips' so they didn't have to take as much out for Social Security. Is this legal?

[TomD8]

From the IRS:

"When you receive the tip report from your employee, use it to figure the amount of social security, Medicare and income taxes to withhold for the pay period on both wages and reported tips. You're responsible for paying the employer's portion of the social security and Medicare taxes."

https://www.irs.gov/taxtopics/tc761