If your employer was provided the information for the tip-splitting, how much to each person and their name, then those amounts should be on the W2 of the recipient. You can check with your employer and request a corrected W2 if you are confident you are being taxed on other employees' tips.
For 2017, I have included a link here for you to use to report the tips you received and the amount given to others every day/month. You can use them daily and then provide a monthly/weekly total, as required by your employer.
That being said, if you find that you are actually paying tax on tips you did not receive, a deduction for job expenses would be used if you can itemize deductions. Job expenses fall into a category where the combined total of miscellaneous expenses must be greater than 2% of your adjusted gross income. The excess can be added to other itemized deductions. I have provided a quick checklist for you to review.
I also attached a copy of the standard deduction amounts for most people based on filing status.
