How much would it cost to file an amended return? I'm ready to file but waiting on one small K-1. I'd like my refund asap.

There is no additional costs for you to amend your return.  Here is how to amend your 2019 return:

In order to file an amended return, make sure that your 2019 return was accepted in TurboTax Online or paper-filed through the mail by the IRS.

To prepare an amended return through TurboTax, follow these steps:

1. Sign in to TurboTax.
2. Scroll down to Your tax return & documents (you may need to select Show), select 2019 and then Amend (change) return.
3. Select Amend using TurboTax Online.
4. Carefully follow the instructions. Don't worry if your refund changes to $0. This is normal on amended returns.
5. When finished, we'll give you instructions for printing and mailing your amended return as amendments can't be e-filed.

If you originally filed using the free version and the amended version caused you to need a more advanced version it would require payment. 

I would suggest contacting us by phone by clicking here and an agent can look into this further.