Thanks for your swift response, @Christine2018.

Yes, you're right. This is why we don't recommend uploading bank data manually whenever there's an on going investigation as there will be a tendency of duplicate transactions when the issue is resolved. 

I understand your needs and demand of your business to work on your December transactions. You can opt to upload your bank data manually. Check out this article for more detailed steps: Import bank transactions using Excel CSV files. 

In case you will have duplicate bank transactions moving forward, follow this article as your guide: Exclude transactions downloaded from your bank or financial institution. 

Feel free to visit again if you have more questions. We're delighted to provide additional help.