CN code 620343 covers men's and boys' trousers of synthetic fibers, other than knitted or crocheted, including bib and brace overalls, breeches, and shorts. Synthetic fibers include polyester, polyamide, and acrylic. Polyester trousers form a significant segment of workwear, uniform, and woven sportswear. Classification requires the synthetic fiber to be the predominant fiber by weight. Trousers from polyester-cotton blends where polyester predominates are classified under this code. The product must be woven - knitted synthetic trousers are classified under Chapter 61. Trousers imported as standalone articles are classified separately from suits.

Synthetic fiber trousers are subject to labeling requirements of Regulation (EU) No 1007/2011 with percentage fiber composition. REACH restricts disperse dyes used for polyester, PFAS substances in water-repellent finishes, and formaldehyde. Workwear and uniform trousers from polyester may contain flame retardant substances subject to additional REACH restrictions. Metal components - zippers, buttons, rivets - must comply with nickel release limits. The GPSR requires product traceability and safety documentation. Trousers intended for wearing in elevated-risk work conditions may be subject to additional requirements as personal protective equipment (PPE).

Synthetic fiber trousers imported into the EU originate mainly from China, Vietnam, Bangladesh, and Turkey. China dominates the export of workwear and uniform polyester trousers. Customs documentation must precisely describe the trouser type, fiber composition, and intended use. Customs authorities may take samples to verify composition. Import of workwear trousers with additional protective properties (e.g., reflective) may require classification as protective clothing under a separate tariff heading. Origin rules require double transformation. Tariff preferences depend on the country of origin and trade agreements - EVFTA for Vietnam, EBA for Bangladesh, customs union for Turkey.

Woven trousers under CN 6203 43 from Chapter 62 imported from outside the EU require a customs declaration in the national import system. Documentation includes a commercial invoice with goods description, packing list, certificate of origin (EUR.1, Form A or invoice declaration) and fibre composition certificate. Customs value is determined using the transaction value method. Duty calculated on CIF value forms the base for import VAT calculation.