Good news, this is now possible 
To return a deposit that was taken outside of using Breww, you can now go to the customer you want to return a deposit to → Containers & uplift orders → Scroll down to the Incomplete container deposit returns section → Return unrecorded deposits.
From there, you can select the invoice to apply the deposit return to, the scheme to use, and the number of containers returned (i.e. the number of deposits to return).
We hope that helps, and as always, if you have any feedback, please let us know!