What to call your boss, subordinates and co-workers at the office
For calling your boss or seniors at the office, you are to use their title instead of his/her family name. For example, if you have a boss whose name is Mr. Suzuki and is a section manager, you can call him just “Kacho (=Section manager)” or “Suzuki Kacho” in office.
For calling your subordinates or co-workers, you are to use their family name with -san.
If you have a co-worker whose name is Mr.Tanaka, you can call him “Tanaka-san”. Seniors sometimes use -kun” for calling male subordinates, like “Tanaka-kun”. Since Japanese people have difficulty in pronouncing foreign family names, first name with–san is often used for foreign workers, for example, Cathy-san” is for the person named Catharine.
Names to use when talking with your clients or people outside the company.
If you need to mention the name of your boss or co-worker in a business talk with clients or people out side of your company, you are to use his/her family name, without –san. If you have a boss whose name is Mr. Suzuki, you are to call him just “Suzuki” with "uchino (means of our company)". The example in such a business talks is;
“Regarding the contract, Suzuki (of our company) reviewed and…..”
Keiyaku-ni tsuki mashite wa, uchino Suzuki ga kentoushi...
Names to use for clients or seniors
For calling your clients or seniors, use his/her family name with –sama instead of -san. –sama is much formal than -san. Using –san sounds too casual for clients and should be avoided.
For politicians, lawyers or consultants, we use “Sensei” instead of “san”, for example, “Suzuki-sensei”. “Sensei” is commonly a title used for a teacher.