Startin 1982 when congress enacted TEFRA, all credit cards tips are now reported automatically. Employee has no option. I remember a senior waiter in the fining dining room of the hotel were I was came to me with his 1982 W2. He said you have made a mistake.. you show I made $35,000 this year. Here is a copy of my 1981 W4.. I had $8000. He had not been paying attention to the memos posted all over the hotel.. near time clocks, in work areas, etc. A lot of career wait people will declare their tips because they are hampered when they try to buy a really nice car or house because their tax returns didn't show enough earnings. Three of those 30 years were in topless entertainment clubs.. very high end.
Cash tips are they only ones that are not provable by the government. The IRS expects to have at least 8% of their individual to be reported as tips received. If credit card tips meet or exceed that, and no cash tips are declared, then no flags are set.
If the difference in reported tips (including credit card tips) and the
8% number are not reported, then the difference shows on the W2 as a separate item. The employee is obligated to include the allocation in the earnings. Failure to do that opens them up to an audit.