The Pay Now option accessed from the sideBar under Clients allows you to Receipt and Allocate to the trip sector in one process

You can choose either Clients, Corporate Client or Trip

In the following example we've selected a Corporate Client - the result of the search displays all trips and sector therein where monies are still owing
You can NOT change the amount to be a Negative value

Select the option to apply the full amount owing - Select the option to clear the amount selected OR just enter the desired amount.
Next select the correct method of Payment, Update the Payment Date (the Amount field is Auto filled)
You can enter or over-type the default Payee
Add the Authorisation Number if available
Add a comment if desired
Then IF all the entries are correct - Select Pay Now