Safe harbor plan with enhanced match and additional match

Looking for confirmation on this to make sure the ADP safe harbor is not violated subjecting plan to the ADP test - 401k plan has an enhanced safe harbor match of 100% up to 6% of compensation. Employer is considering adding a discretionary tiered match based on years of service, so that employees with 15 - 19 years will receive a 100% match up to 1% of pay, employees with 20+ years will receive a 100% match up to 2% of pay. The total match under both formulas for the employees in these higher tiers, for which there will be HCE's, would be 200% up to 1% and 300% up to the first 2%. I believe this creates a higher rate of match scenario and plan has to run ADP, ACP and BRF testing. Or, is it just a matter of running ACP and BRF on the discretionary tiered match?

Thanks for your comments!

ACP and BRF

Absolutely correct - if you have HCEs in 20+ tier and NHCEs in a lower tier (under 15 gets no more?) then you have an HCE getting a higher rate then an NHCE and violate the SH rules.

Assuming that the match was fulfilling the safe harbor requirement, you now have a plan design that is neither 401(k) nor 401(m) safe harbor.  So ADP, ACP and BRF testing are all required.

OP said: "401k plan has an enhanced safe harbor match of 100% up to 6% of compensation."

My understanding of 401(k)(12) is that this matching formula means the plan is not subject to ADP testing (assuming notices are provided timely and the contributions are timely made, etc.).

I don't see where the regulations say that the added extra match eliminates the ADP safe harbor, even if the extra match is based on deferrals over 6% and tiered. Yes, the ACP safe harbor is certainly not met and BRF testing is needed.

What part of the 1.401(k)-3, ADP test safe harbor, am I not interpreting correctly?

For example, my understanding was that you could write in a safe harbor match of 100% of 8% of pay and still be ADP safe harbor, just not ACP safe harbor.

John, the problem is that only some employees receive the extra match. 

All you'd need is one NHCE in a lower match tier and one HCE in a higher match tier and you will have violated Treas. Reg. Section 1.401(k)-3(c)(4) if the match is the safe harbor contribution and Treas. Reg. Section 1.401(m)-3(d)(4) regardless of which contribution type is the safe harbor contribution.