How can i activate voucher number?

Hello there, @Markas Ban. It's important to enter all the necessary details of every transaction.

For detailed tracking, QuickBooks Online allows you to enter the voucher number in the Ref no. field when creating an expense transaction. 

1. Select + New. Then select Expense.
2. In the Payee field, select the supplier. 
3. Enter the voucher number in the Ref no. field.
4. Enter all the necessary info.
5. Click Save and close.

Additionally, there are several reports available in QuickBooks Online you can review your expenses. Go to the Reports menu and select your desired report from the Expenses and suppliers section.

Get back to me if you need more help with running reports. I'm always available here to help.