my mom died last year and I am doing her last taxes. She was retired from LA state employees retirement system and they provided a form1099-R. how determine RMD?

[VolvoGirl]

For a pension, it's whatever they send you. Say all of it is the RMD. If you have a RMD requirement it will ask you if it is the RMD. Say yes and enter the amount from box 1 as the RMD amount. The pension doesn't need to calculate any RMD. Anything your pension pays you is considered to be the RMD. Traditional pensions automatically fulfill the rules of an RMD. So just enter the same amount in box 1 for the RMD for each 1099R.

[NCperson]

is the little box checked near Box 7? 

if no, there is no RMD.  it's just a pension. 

if yes, call the Administrator, they can tell you what the RMD was for 2025.