If you are not in when we try to deliver, Royal Mail will leave a card saying they've called, but no one was at home. It will have full details on either re-arranging a delivery or options for you to collect from a nearby Post Office.
Alternatively you can ask them to leave the package in a 'safe place' - i.e. in the porch, with a neighbour etc. Simply enter your designated place under delivery instructions as part of your order. Please note that this is at your postman's discretion and not guaranteed.
Learn more here.