My wife, in her 401K, contributes the max and on top of that adds after tax contributions. When she turns 70 and we calculate the RMD do we include the after tax amount in the calculation?
The minimum distribution is not affected, but the taxable amount of that distribution will be affected.
Nate_R is correct. RMDs are based entirely on balances in tax-deferred plans. After-tax contributions are treated the same as any other investment outside of a tax-deferred plan. Caveat; be sure to segregate after-tax funds from any rollover you may do with the 401K. Makes accounting much simpler. Fidelity will do this for you, no hassles, if you roll over into an IRA with them.
If you are working past 70 years, you are not required to have mandatory withdrawal from your 401K. RMD is from traditional IRA ( before tax or tax deferred contribution). Roth IRA or after tax contributions do not have RMD.
Over the years, both my wife and I have moved separate IRAs and 401k and 403b to one custodian, Fidelity. We also, have completed our Roth IRAs though Fidelity. Having one custodian really simplifies the RMDs - only one place to pull annual monies from.
I also, have one small inherited IRA (BDA - beneficiary distributed account) from my mother. Something I did not know was that once the "factor" (for me - Single Life Expectancy Table) was determined, eg 20.2, each year it is incremented down by one, so 19.2, then 18.2, etc. I thought you were supposed to go back to the chart each year, which is wrong. Live and learn
401k usually has a Roth option. Seeing as your wife makes after tax contributions, the portion directed to the Roth account is not subject to RMD. Your question says she contributes the max but does not tell me if part or all of the max is going to pre or post tax Roth. If you are asking if the part of the contribution that exceeds the max contribution limits being directed to an after tax account is subject to RMD, the answer is the tax basis ( the sum of the after tax non Roth contributions) is not subject to RMD but the gains will be.
Just a note for the record: The RMD on the Fidelity page is not dynamic. Nothing to do with this thread necessarily but I moved the last of an inherited IRA (I was waiting on a non-publicly traded REIT to close and pay out), The funds went into the account super slick, zero issues. The fido displayed RMD did NOT change - so I asked. Nope, I will need to increase my 2018 RMD to compensate, using my own calculations. Safe to overshoot just a tad. In December of course.
