To improve visibility & security we send all our orders on a tracked & signed service & therefore require a signature from the recipient (unless in special circumstances such as COVID-19).
If you are not home when your order is being delivered by Royal Mail, then the postman will leave a card through your letterbox advising how to organise a redelivery or how to collect it from your local delivery office.
If you are not home when your order is being delivered by Parcel Force you can use the Parcel Force website to re-arrange a delivery date & time that suits you.