Does the Plan Document currently not allow for match or has the company simply not made matching contributions in the past?
Because I think the two may lead to different results. If the plan currently allows for a discretionary match but they haven't made one, the plan probably already has a testing method (current or prior) and I don't think you can used the assumed 3% prior year rule. If the plan doesn't currently allow for matching contributions and you are amending that in with the after tax, then I agree if you elect prior year testing, the first year NHCE ACP is assumed to be 3%.