I have three deleted deposits that had been reconciled. My checking beginning balance is off now. Is there a way I can undo those three deleted deposits?

Greetings, @andrewspire.

You can view the Audit Log to see the details of the transaction. Then, manually recreate it.. I can guide you on how to do it.

1. Go to the Gear icon ⚙.
2. Select Audit Log.
3. Hover to the Show only these events radio button.
4. Tick the Transactions checkbox.
5. Mark the Deleted/Voided Transactions from the Show drop-down.
6. Hit Apply.
7. Choose View.
8. Click the arrow on when it was created and deleted.
9. Take note of the transaction details.

Once completed, you can directly add the transactions in the account's register. Here's how:

1. Go to Accounting menu.
2. Select the Chart of Accounts tab.
3. Locate the appropriate account.
4. From the Action column, click View register.
5. Under the Date column, select Add Deposit from the drop-down.  
6. Enter the correct transaction date, then fill in the remaining fields.  
7. Click Save.

Now, you can start reconciling the manually added transactions. You can read through this article to learn more details: Reconcile an account in QuickBooks Online.

Lastly, you can run the missing reconciliation report to help you locate the previously-reconciled transaction is no longer marked as reconciled

Keep me posted if you have other questions or concerns. I'm always here to help.