Adding True Up Feature Mid Year

Can a plan add a true up provision mid year? Seems like they should be able to, as it benefits participants...

Yes.  Often times this happens simply (an unintentionally) as a by-product of a mid-year change to the frequency of funding the match to something other than on a payroll period basis.

Is it a Safe harbor plan?

If its a SH plan, IRS Notice 2016-16 Section IIID applies to your facts.  You have some time, but must act.

I was thinking same thing. If a SHM then adding the true-up changes the terms of the SHM and that may not fly - but I defer to others with more expertise in this area. 

One might think this doesn't hurt anyone and only helps, but if I'm smoothing out my deferrals to make sure I get the full match and then you change the terms such that I could have frontloaded my deferrals for the year (like from a bonus) and still got the full match of 4% of my pay, then I have certainly been disadvantaged. If this is done to accommodate HCEs who actually did frontload deferrals to get them invested sooner, then I also think you have a potential discrimination issue whether plan is SHM or not, IMHO. 

2 minutes ago, FORMER ESQ. said:

IRS Notice 2016-16 Section IIID

1 minute ago, CuseFan said:

but I defer to others with more expertise in this area.