For ESPP sale, I have completed steps of filling out the lot information in the income section. Now it is asking me to fill out an Employer Stock Worksheet? Why?

[DDollar]

That's because the taxation of ESPP shares has several variables that determine whether any gain is long term, short term, or treated as ordinary income.  It depends on how long you hold the stock from the date of the ESPP plan start, and the date the shares were purchased.