I have made 'bank accounts' by mistake as I have been learning to catagorise transactions. I can see that i can 'make bank account inactive' will I lose the transactions?

Let me provide you with some details and explain more about how inactive accounts affect your transactions, Immbox.

You'll never lose the transactions when you make an account inactive. Rather, transactions associated with any deactivated account stay intact. However, if you're looking to make a banking account inactive, it's better to disconnect it. With this, QuickBooks stops downloading new transactions, but your existing accounting data won't change. 

But, you're unable to edit a transaction associated with an inactive account. You'll have to restore the account first, then analyze the account and correct it to a zero balance before deactivating it. 

Also, you'll have to correct the balance to zero before making a balance sheet account inactive. If it's not zero, QuickBooks will make an automatic adjustment entry to zero out the non-zero balance of the inactive account. Therefore, the automatic entry posts to the Opening Balance Equity account, which is the equivalent of posting to previous years, giving incorrect tax information results when filed.

Aside from that, if you make an account with a balance inactive, QuickBooks creates a journal entry. To give you more details on how the remaining balance moves to another account, read this article for your reference: Make An Account Inactive on your Chart of Accounts in QuickBooks Online.

In addition, you can review categories for automatically downloaded transactions on those active accounts and reconcile them so they always match. Check out this handy article on how can do it: Reconcile an account in QuickBooks Online.

Keep us posted if you have further questions about inactive accounts. We're here to cover all your needs.