How do I fix and change the bank account assigned to past payroll transactions?

I can help you with changing the bank account assigned to your past payroll transactions, @sinead1.

You can update the bank account where your direct deposit and payroll taxes are withdrawn from. Please note this will only affect future transactions. Refer to this article for more information about changing your bank account: Change your payroll bank account. 

Since updates to posting accounts only affect future transactions, you can change the bank accounts by entering journal entries.

Here's how to create a journal entry:

1. Go to the + New button and select Journal entry.
2. Enter your debit and credit amounts. You may also seek advice from your accountant on what account to use.
3. Provide all the necessary information. 
4. Click Save and new or Save and close once you're done. 

In case you'll need to update your Expense and Liability accounts that are affected when you create a paycheck, make a tax payment or create a deduction, refer to the following article on how to view and edit it: Payroll accounting preferences. 

I'm always here if you need further help in changing your bank accounts. Just let me know in the Reply section below. Keep safe and have a wonderful day!