My iMac has High Sierra 10.13.6 but TurboTax Deluxe requires 10.14. I can't upgrade. What do I do?

You can use the TurboTax online editions for the 2020 tax return with your current Mac OS - https://turbotax.intuit.com/personal-taxes/online/

If you already purchased the TurboTax desktop software -

Go to this TurboTax website to request a refund for the software purchased from TurboTax - https://support.turbotax.intuit.com/forms/refund-request.jsp
Use this TurboTax website to check your orders and payments -
https://turbotax.intuit.com/personal-taxes/cd-download/order-status/

And FYI - If you can't  install Turbo Tax Desktop program you can transfer from your 2019 return from your computer into the online version. You need to have the file ending in.tax2019 on your computer.

If you used the Desktop program last year here’s How to transfer into the Online version, expand the blue link if you used the CD/download last year (it hasn't been updated with the new dates yet)

https://ttlc.intuit.com/community/entering-importing/help/how-do-i-transfer-last-year-s-return-into-turbotax-online/00/25953

If you used the Desktop program before you may notice several differences and not like the online version.  It has less features and no Forms Mode.  You can only do 1 return.  Your return is only saved online so be sure to save both the .tax2020 data file and the pdf file to your computer when you are done.  In case you need to amend in the future or if you need a copy to get a loan or something.  You might not be able to access your online return when you need a copy.

I have used turbotax for years but this year since my Mac is MasOS10.13.6 I can not use the turbotax deluxe I purchased at Staples.  I want to continue using turbotax but I can not purchase a new computer just to do it.

If you are having issues and need assistance, please contact customer support. Please see the Customer Support phone number below:

https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632

If you would like to reach out through our website, please see the TurboTax FAQ below for contact information: https://support.turbotax.intuit.com/contact/