I have an IRA account that has pre-tax as well as post-tax contributions. I was thinking of moving my pre-tax balance into my current 401k and the post-tax into the Roth IRA. Does the IRS allow such a thing?

I only see an year-end Form 8606, which doesn't look at each transaction but just net annual movements so thought this would be possible.

I think it is possible, but I am curious how the IRA has BOTH pre-tax and post-tax contributions.

You might be confusing pre-tax / post-tax with deductible and non-deductible contributions.

In any event, you should get professional tax help to help you do it.

ATE