How To Edit A Receivable

Receivables are not locked based on any status, they can be reduced, increased, or edited in general at any time.

The status bar will tell you if the Receivable has been Used, Partly Used, or Unused.

Once you have selected the Receivable to edit, click on the pen/edit icon in the right of the blue bar.

Make your changes to the Receivable here but note that reducing the amount applied will result in the status changing to Partially Used, removing it all together will change the status to Unused, etc

You can add additional invoices to the Receivable as well.  This too will update the status based on your action.