How to undo the bank reconciliation for previous year.( 2018/2019). it's not appears in the history. Can you please clarify?

Hello Rajeega91, 

Welcome to the Community page, 

When it comes to trying to undo a bank reconciliation for the previous year you are unable to do this yourself, you will need to reach out and speak to your accountant as they are the only ones that have the tool to be able to undo any reconciliations that are done and need redoing. 

In Quickbooks the history defaults to the last 365 days, this can be changed on the drop-down at the top of the reconcile history page. 

So it is accounting tab left-hand side>reconcile>top right corner click history by account>clcik drop-down of report period to what you need to view so the 2018-2019 year.