Solo 401k Contributions Timing and W-2 Details

[Francis]

An S Corporation with the same person as sole owner and only employee has a Solo-401(k) that's been in place for a two years.  (1) Can employee deferrals and employer contributions to the Solo-401(k) be made after 12/31 but before the owner/employee files her tax return?  (2) Also, does the W-2 for the owner/employee need to document the elective deferrals? 

[Lou S.]

Deferrals had to come from his W-2 wages and be reflected on his W-2.