Aatrix is recognizing $118,500 as a prior year's limit which is true, that was the 2016 limit.  

The 2017 limit was increased to $127,200 for 2017:
https://www.journalofaccountancy.com/news/2016/oct/social-security-wage-base-2017-201615372.html.  

The employee should have continued to be taxed up to the 2017 limit because those wages beyond 118,500.00 are still taxable.  


Create a Historic entry to correct box 3 (and 4 if necessary) using the steps in the W-2 wizard: