CommunistFinanceBro: No. Employee elective deferrals apply to the year of the earned income from which the elective deferral is made. Elective deferrals from income earned in 2019 are 2019 elective deferrals.
For a self-employed individual, the election to make elective deferrals must be made by year-end and generally must be deposited by January 15 of the following year. However, the deadline for making employer contributions is the due date of the tax return, including extensions.
