Setting up an existing company on QB. The bank transaction downloaded back to 1-1-20. I want to start on 1-1-21. Can I delete the 2020 transactions?

Welcome to the Community, @kevin-centraldis!

Yes, you can delete old transactions when you transfer them to exclude tab, make sure to back up your previous Bank transactions.

Here's how to exclude transaction: 

1. Select Banking.
2. On the Banking page, select the For Review tab.
3. Select the checkboxes of the transactions to exclude.
4. From the Batch actions drop-down, choose Exclude Selected.

To review bank and credit card transactions after you download them into QuickBooks Online, you can refer to this video article: Match and categorize bank transactions in QuickBooks Online and Set up an account for Bank Feeds.

For any additional concerns about QuickBooks set up, feel free to reach out to us. Thanks.