"Your Coinbase file will be compatible as long as it's under 2251 transactions."
This is not true. It is not compatible.
This is the error I get on Turbotax after uploading the CSV from Coinbase:
We couldn't upload your CSV
Please make sure your CSV file has columns for Currency Name, Purchase Date, Cost Basis, Date sold, and Proceeds, then try uploading again.
Coinbase-2020-taxes copy.csv
No headers found in this file.
