Society guidance says that it is ok to make an emergency supply, and then to deduct the quantity of the emergency supply from the quantity ordered on the prescription. Obviously, all the relevant entries in the prescription register must be made.
In such cases it is up to the pharmacist to decide whether to charge for the emergency supply, or make a charge and refund it on production of the prescription.
See Lynsey Balmer's (Head of Professional Ethics at RPSGB) response in the PJ (Vol 275; No 7360; p138; 30 July 2005): (
PJ Online | PJ Letters | Emergency supplies)