Amending a plan to make part time Participants un-eligible???

Plan currently has no excluded employees. Client want to "exclude" most ACTIVE part-time employees by Amending the plan to use the "20 hours per week" exclusion.

This idea makes me uncomfortable. Seems more like a violation of "once-in always-in."

And, I also understand the related issue of the 20 hour per week rule being impacted by the LTPT rule.

Consider that written plan’s provision might govern the plan, even if the provision is not needed for the plan to meet conditions for § 403(b)’s tax treatment. And if a plan is stated using an IRS-preapproved document, a user might have adopted a provision that a plan’s sponsor might otherwise not have intended.

If the written plan does not state a “once in, always in” or other restraint against a change, a plan sponsor might consider whether a change would fit with a more-likely-than-not or substantial-authority interpretation of relevant tax law. Or, many plan sponsors might follow the Treasury’s interpretation [hyperlinks below], even if one considers it unpersuasive.

26 C.F.R. § 1.403(b)-5(b)(4)(iii)(B) https://www.ecfr.gov/current/title-26/part-1/section-1.403(b)-5#p-1.403(b)-5(b)(4)(iii)(B);

Relief from the Once-In Always-In Condition for Excluding Part-Time Employees from Making Elective Deferrals under a § 403(b) Plan, Notice 2018–95, 2018-52 I.R.B. 1058 (Dec. 24, 2018) https://www.irs.gov/pub/irs-irbs/irb18-52.pdf.

I say nothing about what is a correct or incorrect, or persuasive or unpersuasive, interpretation of the Internal Revenue Code.

This is not advice to anyone.

Are you goint to terminate participation by all presently employed part-time workers, or only new hires?  

What if a part-timer goes to 21 hours and then drops to 18, and then to 24?  Oh, the paperwork, the accounting, the disgruntled employees. 

Would what you plan impact only the Sponsor's matching payments, or would the Participant's deferrals be terminated as well.

Is it part time or part-time. One is an adjective and one is an adverb.  Get it wrong and somebody will sue you.