I have a customer who incurs expenses on my behalf, how do I accept a payment from them and clear out expenses?

Hi there,

Welcome aboard to the Online Community, rphenley. I'll be happy to assist you with this. 

Let’s record the partial payment by going to the Receive Payment window. I can guide you through the steps.
 

1. Click the Plus icon in the upper right hand and choose Receive Payment.
2. Select the correct customer.
3. Input the date when you received the amount and the payment method.
4. In the Outstanding Transactions section, mark the box of the invoice you’re working on and enter the amount in the Payment field box.
5. Click on Save.

Give this a try and let me know how you make out. I'll be on standby in case you need further assistance.