I'm new to Quickbooks and have a query about the transaction reports, why do some transactions not show a COA number, how does that happen?

If a COA number isn't attached to your transactions, you can't be able to view it in your report in QuickBooks Online, louise. Let's go ahead and double-check if you've linked it to one.

You can assign numbers to your accounts in QuickBooks Online. To check if they're connected to one, you can follow these steps.

1. Head to the Gear icon.
2. Select Chart of Accounts.

From there on, check if all of your accounts have any digits linked to them. If none, you can add one. I'll show you how.

1. Go to the Gear icon, then Chart of Accounts.
2. Click the pencil icon beside the printer. 
3. In the Number column, write a specific number for this account.
4. Click Save.

For reference, you can read this article: Use account numbers in your chart of accounts in QuickBooks Online.

If you want to break down your expenses and other account types into more, you can read this article for guidance: Create subaccounts in your chart of accounts in QuickBooks Online.

Hit the reply button if you have other questions about why your transactions don't contain COA numbers. I'll be sure to look into it.