7.Until what date must an employer retain the following documents?

a.W-2s issued to employees for 2019

b.A 2018 Form 940 filed on January 31, 2019

c.A former employee's 2017 W-2 that had been returned as undeliverable

d.A W-4 submitted on March 9, 2018

e.Employment applications

f.A cancelled check remitting payroll taxes for September 2014

g.An I-9 for an employee an employee who was hired September 9, 2016 and quit December 7, 2018

h.An I-9 for an employee hired March 14, 2018 and fired November 14, 2019