"Engaged in tax business" refers to engaging in tax collection and management, planning statistics, tax laws and regulations research, policy implementation and interpretation, tax inspection, inspection and investigation, case handling and investigation, tax-related matters handling, and specialized in tax theory research, publicity and education.

"Engaged in tax agency business" refers to directly engaging in agency business in tax agencies and engaging in business work in registered tax agent management institutions.

"Engaged in tax work" refers to directly engaging in tax business in tax departments or other units.

Documentary foreign trade certainly does not belong to "tax-related work"