When OFCOM allocate telephone numbers in accordance with the National Telephone Numbering Plan, they must specify whether an allocation may be transferred from one person to another, and may set out the conditions under which the allocation may be transferred.

If OFCOM allocate telephone numbers for a limited period of time, the limitation must be objectively justifiable in relation to the services to which it relates, taking account of the need to allow for an appropriate period of investment amortisation.