A reference number printed on food packaging identifying the specific production batch, also called a batch mark, required on food labels in the United Kingdom and many other jurisdictions. It typically encodes the production date, line, and shift in a compact alphanumeric string, allowing manufacturers and regulators to trace any unit back to its exact production run. When a safety issue emerges, the batch code transforms a vague problem into a precise recall, pulling only affected stock rather than entire product lines. Consumers can use it to check whether a product they bought falls within a recall notice. In an era of complex supply chains, this humble printed code is the backbone of traceability, the thread that connects a supermarket shelf back to a factory shift.