商務檔案包括帳簿、銀行結餘對數單、進支結算簿、會計師報告、資產損益表、匯單簿、支款及轉賬單、來往數簿、法律文件、稅項及各類繳費收據、信件、會議紀錄等。最早的年份是1915 年，而以1940 年代和1950 年代數量最多。余仁生在經營中藥進出口批發和零售生意的同時，也從1910年代至1960年代初為旅居東南亞的華人提供匯款服務。資料中有很大一部分記錄了香港總公司與馬來亞和新加坡各附屬公司之間的貨幣兌換和款項轉移，以 1940 年代和 1950 年代最多，當中 1948年的客戶匯單共有28冊，佔余仁生檔案箱六分之一以上的空間。

文件中有余仁生（香港）簽發的大量支款單和來往轉賬單，授權支付寄銷貨品的包裝、運輸、關稅和保險、廣告費用等 (1963－1965)，亦有就藥材批發及零售開立的發票和收據 (1948、1956)。 此外，還有一疊共117 張資料清單，列出製造余仁生各行銷藥品所需的成份、用量和價格等 (1959)。

收據中有相當數量來自戰前的稅項。稅款由1925 年至1938 年間廣州市政府以不同名目徵收，用以資助地方政府在警隊經費、警餉費、服裝費、軍費、消防、防空、築路、貧民教養、認銷金融庫券及其他開支。

Contained in this series are various business documents of Eu Yan Sang including account books, bank　statements, incomes and expenses record, auditor’s reports, profit and loss accounts, remittance books, payment vouchers, trading record, tax and various payment receipts etc. the earliest dated year of which is 1915 and mostly in 1940s and 1950s. While engaging in the import/export wholesale and retail trade of Chinese medicine, Eu Yan Sang also provided remittance service to Chinese sojourners in Southeast Asia from 1910s till early 1960s. A significant portion of the materials in this series relates to currency exchange and transfer of money between its head firm in Hong Kong and affiliated firms in Malaya and Singapore with bulk in 1940s and 1950s. There are a total of 28 customer remittance and savings account books of 1948 occupying more than one-sixth of the archival boxes for Eu Yan Sang.

There is a large quantity of payment vouchers issued by Eu Yan Sang (HK) authorizing payments for packaging, shipping, transportation, duty and insurance for consignment goods as well as advertisement expenses in 1963-1965. Invoices and receipts pertaining to the wholesale and retail trade of Chinese medicine (1948，1956) are available. Also kept in this series are 117 information sheets listing out the ingredients and quantity required in the making of the firm’s unique medicinal products with sale price for each item at the time (1959).

Among the receipts kept by Eu Yan Sang, a considerable amount arises from pre-war tax items. These taxes are imposed by the then city government of Canton from 1925 to 1938 under different tax names primarily used to fund local government’s expenses on police food and uniform, militaries, firefighting, air defense, road building, education for the poor, bond subscription and more.