Subheading 999900 applies to dutiable merchandise recovered from vessels that sank in US territorial waters. The goods are treated as imports at the time of recovery, and duty is assessed on their dutiable value. This is a narrow, event-specific provision distinct from standard import entries.

Census estimates the aggregate value of import transactions below the formal entry threshold — currently shipments valued under $800 — and records that total under 999995 rather than distributing it across commodity codes. This ensures national import totals are complete even though individual low-value shipments are not itemized by product.