|Supplementary Planning Documents||
Supplementary Planning Documents (or SPDs) are prepared by district or unitary authorities, and form part of the Local Plan for an area. SPDs usually provide more detail on policies in Development Plan Documents (DPDs), for example on design or local affordable housing policy. They are not a part of the formal development plan, but are a material consideration when deciding on a planning application. Because they are not part of the development plan, SPDs do not have to be consulted on as extensively as DPDs, and do not undergo Sustainability Appraisal or independent examination. An SPD is also known as Supplementary Planning Guidance.