item not arrived - advice needed on claiming back from Royal Mail

[thatlldonicely]

just need a bit of advice please - an item i sent out by royal mail has not arrived & i need to give the buyer a refund. If i do this before the 15 day period the RM use to define a lost item can i still claim for it or do i need to ask the buyer to wait the 15 days in the hope it turns up. - thanks

[LavenderGreen14]

you can ask them to wait 15 days, but most won't. How long ago was it sent.