our business office; this office
Used in formal business correspondence or announcements to refer to the speaker's or writer's own business office. The prefix 当 (とう) means 'this' or 'our' in a humble, self-referential way.
Our business office will change its operating hours starting next month.
Please contact our business office for inquiries.
当店 is a more general term for 'our shop/store', while 当営業所 specifically refers to a business office or branch office.
弊社 is a humble term for 'our company' as a whole, whereas 当営業所 refers to a specific office or branch within the company.
Compound of 当 (とう, 'this/our') + 営業所 (えいぎょうしょ, 'business office'). The prefix 当 is commonly used in formal business Japanese to refer to one's own organization or location.