How do I change the start date of my linked bank account from 1/1/2021 to 1/1/2020?

The bank's start date in QuickBooks Online is the opening balance or the first transaction., usermom5doc30.

You can go to your Chart of Accounts and edit the date from there. Here's how:

1. Go to the Accounting menu and select Chart of Accounts.
2. Click View register under the Action column.
3. Look for the earliest transaction or opening balance entry, then click on it. 
4. Click Edit.
5. Change the date and click Save. 

Just in case you did not enter an opening balance, you can create a journal entry to record it. Follow the steps in this article on how to do it: What To Do If You Didn't Enter An Opening Balance In QuickBooks Online.

You can also check out this article to categorize your downloaded transactions: Categorize And Match Online Bank Transactions In QuickBooks Online.

Don't hesitate to reach out to us again if you need more help.