Money Sources & Taxes - does it matter

Takeover 401k PS plan - never had a TPA apparently.  There has never been tracking of balances by money source (401k & PS only). Terminated participant wants to take a full distribution. For tax purposes upon distribution only, does it matter that there are no defined balances between sources?

Unless some of the deferrals were Roth, I cannot think of any tax difference if it is going to be either distributed in cash or rolled over. For example, distribution will cleanse the deferral dollars from the pre-59-1/2 distribution restriction.

Don't you have to determine whether the participant is fully vested in the PS source? If so, it should not make a difference. If not, how can you make this without going back and tracking balances?

And there are other things to ask about (whether or not it seems likely): loans, QDROs, hardship withdrawals ...

Vesting is not an issue.

But yes, all reasons in favor of TPA's over CPA's administering plans.

Ken - part of the point of my question is it is either: 1. Impossible to back to accurately determine specific balances, or 2. It could be possible, but would be quite costly to the Plan Sponsor.