Raymond K said:

client has a positive balance of  $1466.25.

Assuming that the customer balance is showing as a credit note or a prepayment on one or more Pay Later invoices,

Post receipt of a 'negative' credit card payment against the customer balance owing. 

create a credit invoice, say 500$
receive a cash payment, deposited to a 'clearing bank account'

create a vendor, slightly different than the customer (add a .)
make another payment by credit card, expensing the clearing bank