Still working with my empyloyer. However, I found that you can make retroactive contributions to 401K for 2017 until April 15, 2018. So, the D17 entry on my 2018 W2 corresponds to 2017 make up contribution. In this situation, should I get a corrected W2C for 2017 (with the updated 401k amount in 12b) and another W2C for 2018 (excluding the D17 entry).
