Unreported Social Security and Medicare Tax From Form 4137
Enter the total of any taxes from Form 4137.
If you received tips of $20 or more in any month and you didn’t report the full amount to your employer, you must pay the social security and Medicare or railroad retirement (RRTA) tax on the unreported tips.
Don’t include the value of any noncash tips, such as tickets or passes. You don’t pay social security and Medicare taxes or RRTA tax on these noncash tips.
To figure the social security and Medicare tax, use Form 4137. If you owe RRTA tax, contact your employer. Your employer will figure and collect the RRTA tax.
You may be charged a penalty equal to 50% of the social security and Medicare or RRTA tax due on tips you received but didn’t report to your employer.