When a benefit accrual rate is reduced prospectively or frozen, DoL regulations require a 15-day (or is it 14 day) notice.

Is this notice required when a 401(k) plan changes the employer match from 25% to a match that is at the complete discretion of the employer? Here, the guaranteed match is decreasing from 25% to 0%, but the employer may decide to match at the end of the year.

If this were not a profit sharing plan, the answer would clearly be yes. But since 401k plans are profit sharing plans, is the DoL notice required?

ERISA 204(h) only applies to defined contribution plans to the extent they are subject to minimum funding standards. So . . . a 401(k) plan is not required to give 204(h) notices.

FYI, IRS has just issued final 204(h) regs. Click here to link to them.

No, the 204(h) or 15 day notice would not be required. That notice is only required for plans subject to the minimum funding requirements of IRC 412 such as defined benefit or money purchase plans.

This type of change would be required to be disclosed in a Summary of Material Modifications though.
Also, if the change is being made for this year, make sure this amendment to the match formula was not done after participants had already earned the right to that stated match for the year. (i.e. if there is not an end of year employment requirement)

What advance notices are necessary when reducing the match or making other similar changes (Assuming these changes are prospective)? Does the answer change if doing these changes at mid-year? Any citations?

"blaster" - please re-read the code and regs I pointed out to you earlier.