Did you ever get resolution on this issue?  We now have the same problem with an apparent inability to e-file.

Not through Proseries. We tried mailing it in as allowed by Rev Proc 2024-39 but the IRS people didn't even look at it and sent it back because they are unfamiliar with their own Rev Procs. The firm that helped the client with all of the calculations ended up paying another firm to e-file it in a software that does support the forms. I believe it is cch axcess. 

I've encountered this same ProSeries issue before. 990-T e-filing does not cooperate with Form 3800, and will produce errors regardless if you attach it as a PDF or not.

In all honesty, the easiest ways I've handled this is to do either of the following:

1. Either turn off the error checking and e-file it anyway (the ProSeries way).
2. Or just paper file the return with 3800 and 3468 attached—much less aggravation.

Although the IRS instructions for Form 3800 are quite clear on handling these credits and attachments, it is worth reminding you to take a quick look (IRS Form 3800 Instructions).

I am on my 5th attempt to get 2023 990-T accepted by the IRS!  So frustrating!!

Proseries Professional - 990 Series SHOULD SUPPORT FORM 3800 as it is supported with the 1120-S and 1065.  I have asked multiple support agents to escalate this issue to the programmers... yet, here we are another year coming quick and it looks like 2025's 990-T is NOT going to support Form 3800 AGAIN!

I will tell you my attempts so far (during the past 11+ months!) with hopes someone has a solution to share 🙂

1. Attached pdf Forms 3468 & 3800 - got rejected 11/13/24

2. Mailed to IRS with e-file rejection log 11/14/24 - big red X on the IRS received stamp and returned as incomplete and e-file requirement notice 01/22/24

3. Spoke with IRS agent, told to fax another copy of return with e-file rejection log, my letter of explanation, and IRS notice to EO unit (36 pages) 01/26/25 - IRS letter stating more time is needed to review 03/03/25,05/01/25 and 06/12/25 and then... you guessed it....another big red X on the IRS received date and the entire 36 pages plus another 3 page IRS notice stating the same e-filing requirements and that they cannot process this incomplete 990-T return 07/22/25

4. Multiple calls to IRS and Taxpayer Advocate Service for additional guidance; however, calls were disconnected after being on hold 1+hour or message left asking for a returned call.  Unfortunately no communication as of 10/14/25.

5.  Printed all the above notices, letters, and Form 990-T for mailing with yet another LONGER letter of explanation that included a detailed timeline and quoted Pub 4164 section 6011(e)(3) plus Form 8948 and faxed to EO Unit again 10/14/25 - obviously no response yet being that the IRS is shut down. 

6. Being that it is tax software renewal time.... yep, I pushed for a resolution to the Proseries Professional 990-T Form 3800 issue!  After six or so calls with the Intuit sales rep regarding my renewal, I have been granted access to Lacerte at no charge for this one client's 990-T tax return (through approval of upper management).  A Lacerte specialist joined our call and "assured" me several times stating Forms 3468 & 3800 are supported for e-filing.

7. Of course I was excited to download the 2025 program today.... only to find that the 990 series is not available yet.  Ugh!  Hopefully I will be able to get 2023 Form 990-T RE-prepared, e-filed, accepted and then 2024 Form 990 & 990-T prepared, e-filed and accepted before 11/15/25.

If you KNOW from experience, that Lacerte does in fact support e-filing these forms, please let me know before I spend more hours on this return (and trying to learn a new software).  Otherwise, I will let you know if this works out.  Cross your fingers for me... because then you know what's next... $12,000 late penalty to fight.  LOL <-- smh, I gotta laugh and go with it now, right?

Sorry for the LONG post... I even left out all of the Excedrin and tears involved.

~Paula

Not sure this will help, but you may give it a try. In attaching a pdf and e-filing choose other and just the form number (3800) in the description. I have noticed if I put the word "form 3800" I will get a rejection, but if I just put "3800" it goes through.

Hi @Paula - PS Tax 

Thanks so much for taking the time to share all the details of your experience. We can only imagine how frustrating and exhausting this process has been. You've clearly worked hard and been patient to get this fixed. We know how important it's for you and your clients to have Form 3800 supported for e-filing with the 990/990-T.

We want to assure you that we have submitted your feedback to our ProSeries Development team, and they are actively reviewing this. Your detailed timeline and persistence have been extremely helpful in demonstrating how this impacts your workflow, others, and clients.

We know this has been a long journey, and we genuinely appreciate your continued partnership and understanding as the team works to evaluate and improve support for this form.

Thanks again for sharing your experience with us and for your patience!

Kathi,

I want to say I REALLY appreciate your GENUINE response of understanding and assistance that seems to be so rare these days!  Your assurance of escalating this ongoing issue to the Development Team gives me hope of a speedy remedy and restores some confidence of getting "true support" that we (tax professionals) need from Intuit.

Thank you!

~Paula

You’re very welcome @PSTaxAccounting! As mentioned above, we can only imagine how frustrating this has been, and we’re hopeful that Excedrin and tears will soon be a thing of the past! Thanks again for your patience and understanding as Development looks into possible ways to make things better.