Client rolled over all pre tax traditional IRA  (previously from all,100% pre tax 401K)  back into pre tax 401K. Then made a non deductible traditional IRA  contribution and immediately converted to Roth (back door IRA). Client argues that this is not a taxable transaction since no IRAs are in existence at the time of the Roth conversion. My position is that the funds came from 100% pre tax 401k and the source for the back door IRA came from pre tax,  therefore is taxable .  If some of the 401K was post tax, then we do the math and go from there, but this was all pre tax. The fact that there is no IRAs does not tell the whole story here since the source was 401k to IRA to 401K. OR, does the IRS only look at the value of any current IRA????