商業函件分兩部份： (a) 法律文件：包括香港政府工商署於 1956 和 1957 年簽發給余仁生的生產商牌照和貨倉牌照、 1957和1958年余仁生 (香港)運貨往馬來亞/新加坡時的各類批文包括評稅及搬貨許可證、貨品進口聲明書、貨物出口許可證等，以及七份1951年的貨運保險單。 (b) 信件和便條：包括從馬來亞各市及新加坡余仁生寄給余仁生（香港）的大量信件，計自 1956年至1968年，共有1,278張，當時按信的來源地及日期用金屬文件夾分成數疊保存。此外還有1956年及1961年從馬來亞和新加坡寄返香港母公司的劃一表格和收據，確認收訖匯款、信單及回條。其他零散信件、便條、賀卡、名片和已拆的信封，都存放在這部份的資料中。

Business correspondence is arranged into two subseries. Subseries (a) includes legal papers such as Manufacturer’s Licence and Warehouse Licence issued by the Director of Commerce and Industry to Eu Yan Sang in 1956 and 1957; applications for duty assessment and permits for import and export goods shipped between Hong Kong and Malaya/Singapore in 1957 and 1958 and 7 copies of shipping insurance policy of 1951. Subseries (b) contains a large quantity of correspondence sent to Eu Yan Sang (Hong Kong) from affiliated branch offices in Malaya and Singapore. There are altogether 1,278 letters and were bound separately according to where they were from and in chronological order in the period 1956－1968. Besides, there are remittance-related correspondence in self-designed standard forms directed to Hong Kong office from Malaya and Singapore in 1956 and 1961 acknowledging receipt of remittance. Other loose letters and notes, greeting cards, business cards and opened envelops are also kept under this subseries.