Thank you but that doesn't seem to affect the result.  To elaborate, client has $113,150 in taxable IRA distributions--$67,600 in MT and $45,550 in AZ all coded by state in screen 13.1.  Lacerte apportions $75,433 to MT based on 8/12ths period of residency--.66666667 whereas AZ receives $45,550 based on the state entry coding.  This inconsistency results in an overstatement of $7,833 of pension income on the state returns.  I want Lacerte to include MT income by state coding on screen 13.1 not by using some formula allocation.

(corrected, below)

Hmmm...

Actually, I have 40 years of experience preparing MT tax returns and I can say with certainty that when a taxpayer relinquishes MT residency by moving to another state bringing part year residency into play.  Income is determined by state of residency before and after the date of the move.  Montana cannot tax income earned after the move and AZ cannot tax income before the move.  Question about questionable Lacerte programming still not answered.

@kalo5asmi I think you need to contact support. My guess is that there is some input that is incorrect. I tried to replicate the numbers, but I could not even get the IRA to show up on MT. I don't do MT, so I know I am also missing something.
You can use Ctrl + L to send the return to Lacerte with your concerns, but I think a phone call would be better.

I think you're right.  Interestingly the MT/AZ SS allocation works great and I will use that to jury rig a solution to this problem. Obviously something is amiss in the software which is not too surprising given the myriad of inter-relationships given the number of states and categories of income.  Many thanks for your interest.

I found the wording and stand corrected, that IRA is treated differently than lottery winnings:

"Line 9 – Montana Source IRA, Pensions and Annuities
If you are a nonresident, the IRA distributions, pensions and annuities that you reported on Form 2, line 4b, is not Montana source income and is not taxable to Montana.
If you are a part-year resident, enter all the taxable IRA distributions, pensions and annuities included in your total on Form 2, line 4b, received during the part of the year that you were a resident."

Now - How to get Lacerte to do that.

It is a bit of a conundrum but I made this thread to develop the issue for Lacerte.

I had no idea that a snowbird could take their RMD while in AZ, then spend the rest of the year in MT and not pay taxes on it.

I don't think a snowbirder can. A snowbirder keeps their permanent residence as MT. They just get the hell outta Dodge for the winter, but they intend to come back home after the thaw.
My understanding of this question is that there was a real move from MT to AZ.

We have "part year" residency provisions.

If you leave Dodge for the winter, you are not considered to be a part year resident for tax purposes.

Many people leave Dodge for warmer climes with no intention of returning to a certified tax hell!