Hello Gaeb1995,
It's great to have you join the QuickBooks Community. Rest assured, I'll be happy to point you in the right direction so you can enter a deposit refund with ease using QuickBooks.
In order to accurately record your transactions, I highly recommend consulting an accounting specialist for expert suggestions. This ensures your books remain accurate while you continue to manage your work with peace of mind. You can also get in touch with a professional using this link here. Other accounting professionals are able to see this post in the Community and this will allow them to chime in. In the meantime, I encourage you to check out the following article that shows you how to: Enter supplier credits and refunds in QuickBooks Online.
Let me know if this info helps. I'm here to steer you in the right direction.