I have a client whose 401(k) plan is making a QNEC because they did not pass the ADP test. There is no match in the plan. Their corporate CPA is instructing them that the QNEC is to be used to gross up their salary and then addes to the deferral amount shown on the w-2. I thought they were just additional ER contributions to be reflected in the plan account balances Any help?

The QNEC isn't reflected on Form W-2. That's also a logical conclusion because QNECs aren't subject to the 402(g) limit either.