Greetings, @Baumbach19.

I want to share some details on how you can assigned categories to your transactions in QuickBooks Online.

To start with, there are different ways on how you can assigned specific categories to your transactions.

• • Manually assigned categories to your transactions in the For Review section in the Banking page.
  • In every line item added on the invoice you've created, you can assigned it to a specific income or expense category. You'll just have to set it up when creating Product or service item.
  • You can set a rule so when your transactions are downloaded from bank, the system will automatically assigned a category on it. 
  • If you choose to match the downloaded transaction to an existing transaction (i. e. invoice), there's no need to add a specific category to the invoice payments you've received.

On the other hand, a reimbursed expenses is not an income at all. With QuickBooks Online, you can either make the expense transaction billable and add it to an invoice, or create a journal entry.

If you want to reimburse it through an invoice, here's how to turn on the billable function:

1. Go to the Gear icon.
2. Under Your Company, choose Accounts and Settings.
3. Select Expenses.
4. Go to the Bills and expenses section.
5. Check the option to Track billable expenses and items as income.
6. Hit Save.
7. Click Done.  

    

   

If you want to reimburse the expense transaction through journal entry, you may check out this article for a more detailed instructions: How to Pay for Business Expenses with Personal Funds.

I'd recommend consulting with your account so you'll be guided properly in selecting the proper category for every transaction recorded in the system.

Let us know how it works on your end. I'm always here to help assigned categories to your invoice payments.