Hi - have a 401k plan whereby the 70 1/2 minimum amount for a father of an owner was calculated incorrectly for the last 15 years (TPA didn't include insurance cash value in account balance). if they do not go back and correct for each of the 15 years, can the plan be disqualified or is this an issue that affects only the individual participant? thanks.

70 1/2 distributions are required by Code section 401(a)(9). So it's a plan qualification issue, not just individual tax issue. They'll be looking at filing under EPCRS.

i believe he will be subject to a 50% excise tax penalty on the amount that was not distributed as well.

Was the guy in any other plans, or did he have an IRA? I think you can consolidate accounts from a balance perspective and withdraw the aggregate amount from just one account, if I'm not mistaken.

Unfortunately, you are mistaken. IRA's, yes. Qualified plans, no.