How can I remove/delete records that are older than 31st August 2017?

Hi laura-barrie Thanks for reaching out to us here on the Community. There isn't a method that would enable you to batch delete data. If you have a bank connected and you've added all your transactions in from the for review page then you could select the categorised option and batch undo however this wouldn't remove any transactions that have been added manually to the bank/chart of accounts, these would have to be deleted on an individual basis.

We have submitted your feedback to our developers and hopefully they maybe able to implement in the future an option to delete or archive historical records. We have included a link that would also enable you to leave direct feedback: https://feedback.qbo.intuit.com/

If you need further information or assistance from us please reach out to us and we'll be happy to help you. 

@laura-barrie 

You can use the deleter tool and create a Journal Entry to offset it as a new beginning balance on August 31st.

https://get.transactionpro.com/qbo

Another option, you can purchase a 3rd party service to migrate your data to a new QBO account.