I have two W-2 Forms; is there a maximum Medicare tax or social security tax that can be withheld in a single year?

[pemerick1]

If yes, how much and how do I know if the refund shows on my return?

[BMcCalpin]

There is no maximum for Medicare, but for Social Security, the maximum taxable wages is $118,500 (2016).

If it is the case that neither W-2 was over $118,500 for Social Security wages but was only in the aggregate, the TurboTax will detect that more than $7,347 (6.2% of $118,500) was withheld and return the excess to you as a tax payment on line 71 on page 2 of the 1040.