Deadline for funding deferrals for owners of Sub S Corp

What is the actual deadline for funding their deferrals for 2018?  Is it 12/31 or the due date of the tax return.  They have only partially funded their deferrals throughout the year?  Thanks!

S corp/C corp doesn't matter for this purpose.  Deferrals have to come out of a paycheck(s) by 12/31.  Once that happens you have the timing of deposit issues (e.g. 7 business days for a small plan) but that is a different matter.

On 12/31/2018 at 9:44 AM, Pammie57 said:

What is the actual deadline for funding their deferrals for 2018?  Is it 12/31 or the due date of the tax return.  They have only partially funded their deferrals throughout the year?  Thanks!

I would suggest they actually have fully funded their deferrals throughout the year, because they can only "fund" what they defer.  What they deferred, they funded.  They are all done for the year.  What they apparently didn't do is MAXIMIZE their deferrals for the year; a different animal.  SOL is the answer as Ed noted.