For 2023 return I had to use different software to file & have received my return. I had started it on TurboTax but did not complete. How do I delete this form?

The IRS does not know which tax preparation software you used or the type of tax preparation service you used or care.

You can clear the tax return in your TurboTax account.

If you have not paid for the online edition you are using, have not filed your tax return or registered the Free edition, then you can clear your return. Click on Tax Tools on the left side of the program screen while working on the 2023 online tax return. Click on Clear & Start Over.

Since Online has closed you might not be able to clear it.  That’s ok.  Just leave it and abandon it.  You will probably get marketing emails to finish and file but just ignore them.  They don’t know you filed a different way.