I completed my return, but was told I can't e-file. However before I printed and mailed the return, I noticed an error. Can't I start over instead of amending?

If you have mailed your return, you cant start it over. You will have to amend. 

  To amend your 2019 tax return: Wait to see if your return has been accepted or rejected by the IRS or state. If rejected, you can correct and re-send your return. If accepted you should wait until your return has been processed and you receive your refund or conformation that any tax due has been paid. If you file an amended return while you first return is being processed it can cause extended delays for both returns if two returns are in the system at the same time. In addition, if the IRS makes any change on your original return, you might end up having to amend the amendment. Amended returns can only be mailed - allow 8-12 weeks - can take up to 16 weeks (4 months) for processing. How do I amend my 2019 TurboTax Online return? https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/00/27577 To Amend on Windows. https://turbotax.intuit.com/personal-taxes/cd-download/amend/ty19/

Thanks a lot for your help. That’s not quite what I was asking though. Let me clarif.

As I said in my question, I have not actually filed yet. Just got the generated PDF.

I was asking how I can start my return over, not instructions on filing an amendment. 

I don’t see why I need to file an amendment if I have not yet sent anything to the IRS.