Do you have more than one retirement account that is managed by the payer on the 1099R?
Heck...call the provider of that 1099-R and ask.
I have two 1099-Rs issued from Fidelity...one for a Pension from one company, and one from a 401k from a different company...both handled by Fidelity. There is nothing on the 1099-R forms that indicates which is a 401k...but the original company it represents is at the bottom of the "Payers" address.
But then, I already know which is the 401k and which is the Pension, because my Pension pays the exact same amount every year....and the 401k varies considerably.
I know it is from a 401k, but turbotax doesn't know, and it gives an error. The 1099r form has a box for IRA, and I can check that box and turbotax is ok with that.
This is for an RMD payment. The IRS should have given a box for 401k, because 401k distributions can be used to pay the RMD.
Rephrase question - how does turbotax and the IRS know my 1099r form is from my 401k ? This is for an RMD payment.
I don't know if it does, unless they audit you and require more records at that time.
Or.....perhaps historic records of your contributions every year going into a plan in the first place.
OR...Of course the 1099-R provider also sends a copy of the 1099-R, in some kind of digital format, to the IRS too each year. Maybe that digital file the provider sends to the IRS has some additional info on the account type.
It takes a couple of months...sometimes up-to a year for the IRS to match what you "claimed" in your e-file, or paper file, with their records of what the providers submitted to the IRS separately....after which they may start asking questions if something looks fishy.