Preauth calculations questions

[atd]

I have a couple of questions about how the insurance estimates are calculated for preauths. Here's my setup:
I have 2 patients on the same insurance plan. The insurance is a Medicaid plan - but I have it setup as a PPO plan with a fee schedule and most categories at 100%, a couple at 0%.
My treatment plan estimates for a set of new dentures are correct - it shows the full fee, the insurance estimate based on the fee schedule, the discount as the difference, and the patient portion as $0.
For patient #1: When I created the preauth it calculated the full fee and insurance estimate as it showed on the treatment plan - but the writeoff was $0 and the estimated patient portion was what should have been the writeoff amount.
For patient #2: The preauth calculated the insurance estimate as $0, the writeoff as $0 and the patient portion as the full fee. I tried deleting and recreating, recalculating estimates, etc. and still end up with the same result.

Here are my questions:
1) I can't figure out why these two preauths would be calculated differently when they are on the same insurance plan and I'm sending a prior for the same services.
2) Having the estimated writeoff and patient portion different on the preauth (shown in the account module) than on the treatment plan is confusing. We had a call from a patient asking about their cost for the denture and our staff wasn't sure which was correct.

I did see an old forum post that said writeoffs shouldn't be part of preauths - but I'm not sure why or if that has changed. Any clarification would be appreciated.

Thank you!

[jordansparks]

The two patients really aren't on the "same plan" as far as OD is concerned. Currently in OD a plan is unique to a subscriber. So I'm thinking maybe there is a slight difference in how you have them set up.

[atd]

I have the "Apply changes to all identical insurance plans" checked by default since most of the plans we bill are Medicaid and have the same benefits for every patient. I double-checked both plans and did not see any difference between them. Could it be something with the existing-other denture procedures? Would the Prosthesis Replacement or Prior Date of Placement fields on the claim have any affect on the insurance estimates? I deleted the preauth and created a new one and this time only one of the dentures showed an insurance estimate, the other showed $0 for ins.
Any thoughts on my second question about the patient responsibility calculations?

Thank you

[jordansparks]

For the second question, I would always go by the finalized and archived TP. The preauth is organized for the benefit of the insurance company, not the patient.