Pre-shipment inspection is a quality-control check of a representative sample (around 100 units) performed at the factory in China before the full order leaves the country — and, critically, before the balance payment is released to the supplier. Timing the inspection ahead of final payment preserves negotiating leverage: if defects are found, the buyer can withhold or renegotiate the balance rather than discovering problems only after the goods have shipped and been paid for in full.
Distinct from Same-Day Delivery Physical Sample Inspection (checking a single pre-production sample delivered to the buyer) and from Third-Party Product Testing Services (lab/compliance testing) — this is a bulk-batch check performed in-country, gated to the payment schedule rather than to product approval.