I sold stock from an ESPP in 2017 after the stock split. The 3922 form I have from 2015 doesn't match the qty sold. How do I report the difference in qty?

If you're going to use the ESPP step by step process then simply "translate" all the "per share" figures by the split ratio and increase the # of shares transferred to the post-split figure.  So if the stock split 4 for 1 all the per share figures get divided by 4 and the # of shares gets multiplied by 4.

Tom Young