TurboTax 2020 conundrum re Mac High Sierra O/S

If you installed Parallels you'd could run a copy of Windows 10 inside it w/ the Windows version of TurboTax, or you could run macOS inside it with the Mac version of Turbotax.

The easiest method would be on your 10.13 High Sierra iMac w/ Parallels to install a self-contained copy of macOS. This would be installed via Parallels utilizing your physical Macs Recovery Partition. I'm fairly sure Parallels on a 10.13 High Sierra machine would allow you to install directly a 10.14 or 10.15 Mojave or Catalina virtual Parallels machine directly. However the "worst" case is you would install a 10.13 High Sierra Parallels virtual machine...and then once it's working you'd upgrade the virtual machine to Mojave or Catalina. Either way, this would be the quickest and easiest way to get your a self contained macOS that'll use the Home/Business TurboTax you need. And it would be TurboTax for Mac.

The other option is to in fact install Windows 10 in the Parallels virtual machine. The downside of this is you would need to download the Windows 10 disk image (ISO) file from Microsoft. However, this is very easy and you can do it from here: https://www.microsoft.com/en-us/software-download/windows10ISO

And Parallels would then utilize that image to create a Windows 10-based Parallels virtual machine. If you go this route then you would need to buy TurboTax for Windows. The advantage of this though is that you then have a Windows virtual machine which you could potentially have other uses for beyond TurboTax. The downside is that it is an extra step...but it's not much of an extra step.

How much RAM do you have though? As long as you have 8GB+ you're fine. Otherwise, if you only have 4GB of RAM I'd recommend at a cheap $30 RAM upgrade to bring you up to 8GB total. If you search for "mid 2011 iMac 4gb kit" you can get them for this price on Amazon. If you plan to retire your iMac in the coming months, that's all you need. If you plan to keep it, or give it to a family member, or someone deserving, then you can get an 8GB kit for $50 to have a total of 12GB or even spend $70 to get a 16GB kit.

I had exactly the same problem. After about 30 hours of attempting to use Boot Camp, overriding the Boot Camp plist as suggested in various videos, I ran into a problem creating a bootable USB drive which is required for older Macs. It seems that the Microsoft Windows 10 disk image file is too large for the format requirement of the thumb drive even though the drive was 32 GB. The older (smaller) build version of Windows 10 that was recommended to solve this issue is unfortunately unavailable.

To make a long story short... I downloaded the appropriate trial version of Parallels for your specific Mac operating system (In my case it was Parallels 13) and let Parallels do the job. In approx. 30 minutes the program worked its magic absolutely painlessly. The trial version runs for 15 days before requiring a key code... time enough to see that it will work for you. The bonus of this method is that both Windows and Mac files are easily accessible.

The only problem now is learning Windows, a problem I have avoided since 1987!

It will not be resolved. Your last usable year with turbo tax was the tax year 2019 for Mac. You can use turbo tax 2020 on windows 10 if you have parallels.

You could purchase Parallels and thus be able to run a macOS Mojave virtual machine pretty easily. Their latest version still supports macOS High Sierra. As long as you have 8GB of RAM or more this should run sufficiently well. They do have a free trial to fully test it out. It's $80 if you choose to buy it.

If you install Parallels you can then install MS Windows within that. What Parallels allows you to do is to run MS Windows or other operating systems and their applications) simultaneously as Mac OS. So to answer your question, if you had Parallels running and MS Windows installed in Parallels then you can run the MS Windows version of TurboTax. You could then toggle between running MS Windows and Mac OS without having to restart the computer.

If you need additional info on Parallels please visit their web site.

Turbotax online lets you do complicated returns. Same as downloaded options. Works fine except does not let you view forms until you pay. I guess this is because you could print the forms before paying for the service.

Another option would be to use the online Turbotax do do your taxes this year. Won't need to upgrade the system.

I am in the situation! I have iMac OS High Sierra Version 10.13 ( 2018 ) was purchased and I can’t do my taxes . I got my TurboTax Home & Business at Costco for a total of 85.29 and it couldn’t be installed . It has to be Mojave 10.14 or higher. I end up paying to TurboTax 177 . 00 for the online version and let me tell you something that you have get individually, no any family member or friend can use it ! Getting a new computer is not the solution !

I have been running Paralells and windows 10 for years now on my 27 iMac Turbo Tax always worked fine for me in the virtual World.

TT premier is what I've been using online. Small business version is probably also available.

I wouldn’t purchase a new IMac just for the new TurboTax software, especially when my 2011 iMac runs great and during the pandemic when saving every penny helps. H&R TaxCut will work on Safari 13.1.2 and above.

Yes, TurboTax told me last year that I would have to upgrade to Mojave to use it this year. I just spent hours upgrading to Mojave, and TurboTax now tells me that I will have to upgrade to Catalina to use it next year. If I upgrade to Catalina, I will likely have problems using my old Dell color laser printer, which is 32-bit. I’m getting tired of TurboTax always wanting me to upgrade my operating system.

I have a Windows computer that I bought solely to run Quicken, as Quicken Essentials could no longer run on my Mac when I upgraded to High Sierra three years ago. I guess I will have to use it for TurboTax after this year. I used TurboTax for Windows for years before I bought my Mac, and TurboTax never made me upgrade Windows.

I thought the problem was with Apple not Intuit. I also have a 2011. Considered using the online version of turbotax but it does not have a forms view which I've found that I need. Time to purchase a new imac?

Thanks I added 8gb ram and now have 16gb. I also bought the OWC 1tb ssd drive and installed it. Now my iMac is fast! I still ended up buying TaxCut for Mac for $21 from new egg.

Same here. My late 2013 Mac does everything I need except TurboTax. And Flight Simulator. I plan to get by with another tax program.