internship (of a certified public accountant)
Refers specifically to the practical training period required for a certified public accountant (公認会計士) in Japan. Not a general internship term.
To become a certified public accountant, practical experience as an internship is required.
A general term for internship in various fields, while 業務補助 is a specific legal term for CPA training.
Compound of 業務 (business, duties) and 補助 (assistance, support). The specialized meaning comes from its use in the Certified Public Accountant Act.