Royal Mail typically holds a parcel at the local delivery office or post office for 18 days for collection. After this period, if the parcel is not collected, it will be returned to the sender. For Special Delivery items, the hold period is shorter, usually 7 calendar days before being returned. Additionally, customers can use Royal Mail's Keep Safe Service to securely store packages for an extended period, up to 66 days, for a fee starting from £13.50 for 17 days. In some cases, contacting the local post office may allow for longer holds based on specific circumstances.