承知いたしました

Think of this as your 'work mode' button. You use it when a superior or a client gives you instructions. It usually appears at the very end of a conversation or email. In spoken Japanese, pair it with a crisp bow. In writing, it often stands alone as a complete sentence. You can also add the specific thing you understood before it. For example, use shochi itashimashita after someone explains a deadline.

Use this in any business setting where hierarchy matters. It is perfect for emails to clients or vendors. Use it when your boss gives you a new project. It is also common in high-end service industries. If you are at a fancy hotel, the staff will say this constantly. It makes you sound reliable, polished, and very respectful. It is the safest choice for B2B communications.

Never use this with your close friends or family. It sounds incredibly stiff and robotic in casual settings. Your friends might ask if you've been brainwashed by your company! Also, avoid using it with people younger than you or your subordinates. Using humble language toward a junior can feel sarcastic or confusing. For peers, a simple wakarimashita or shochi shimashita is much more natural.

This phrase is a prime example of Kenjougo or humble speech. In Japanese culture, lowering your own status elevates the other person. By using itashimashita (the humble form of 'did'), you are placing yourself in a position of service. This creates a harmonious social balance. It shows you respect the other person's authority or importance. It is a key part of the 'omotenashi' (hospitality) spirit.

承知しました (shochi shimashita) is the slightly less formal cousin. It is still polite but less 'heavy.' 了解いたしました (ryoukai itashimashita) is common but controversial. Some older bosses think ryoukai is only for peers. To stay safe, stick with shochi. If you want to be even more formal, use かしこまりました (kashikomarimashita). That one is usually reserved for customers or very high-ranking officials.