Form A is an origin certificate used in the Generalised System of Preferences (GSP), through which industrialised countries grant unilateral tariff reductions to imports from developing countries. The Form A was issued by developing country authorities and presented at the importing country's customs. In the EU, Form A has been progressively replaced by the REX system since 2017, where registered exporters self-certify origin via invoice declarations. Switzerland also grants GSP preferences and accepts both residual Form A and REX attestations.