How do I stop expense transactions from previous years from combining with expense transactions for last year ?

I'll help you handle your expenses in QuickBooks Online (QBO), @drainbusterssiou.

I've got two suggestions to stop QBO from combining previous expenses and last year's transactions. First, please make sure to enter the correct date when creating your entries. This way, QuickBooks won't combine them unnecessarily.

If you're running an expense report, ensure to select the right Report period. This way, you can only see the details you need. Here's a sample screenshot for your reference:

Also, you'll want to make sure to close your previous year's books. This helps prevent any accidental changes that could affect your financial reports.

Here's how:

1. Click the Gear icon, and then select Accounts and Settings.
2. Choose the Advanced tab.
3. Select the pencil icon in the Accounting section.
4. Click the Close the books radio button.
5. Enter a closing date. 
6. Select the Allow changes after viewing a warning and entering a password option from the drop-down menu to require a password before editing your closed books.
7. Click Save and then Done.
   

I'm adding this helpful link for more information: Close your books in QBO.

Also, we've collated a year-end checklist to complete your tasks smoothly in QBO.

Count me in if you need more tips about managing your transactions in QuickBooks. I'd gladly help you.