Start of Production is a term used in many sectors, and it is abbreviated as SOP. It means the start of serial production phase, when the affected product is released (both from design and process side), and mature enough for the serial life. Many times SOP is also referred as "Product Launch".

SOP is a major element of the product life-cycle, and a key milestone of the APQP process, by closing the "Product and Process Validation" phase, and starting the serial life of the part.

From the start of production all parts are produced under serial conditions, but these are not the first ones produced that way. In the automotive sector, the PPAP (or 0-series) parts are already produced under serial conditions. To start a reliable serial production, variation and risk must be minimized. To reach this goal, the automotive specific APQP framework has been elaborated by the big three American carmakers. According to the APQP process, the following key elements / points / inputs must be closed to start the serial production:

There are general misunderstandings about the relation of SOP and PPAP. SOP does not start the PPAP production, but comes after it. SOP is only allowed after a released PPAP.

SOP is followed by Start of Delivery (SOD), but this term is not as common as SOP. SOD means the shipment of the first serial produced parts to the customer, of course with serial packaging.