1. Leave time
退社
Sometimes when the regular leaving time has passed and you have finished your work, other people are often still working. Even if you think it's hard to say you're leaving because there are other people left, don't just leave quietly. Use the phrase お先に失礼します (pardon me for leaving first) or お疲れさまです ( thank you for your hard work).

2. Greetings
あいさつ
Also, depending on the situation, you may be able to help those around you by offering your help by saying, 何かお手伝いましょうか (Can I help you with something?). If it's something that you can easily help with, such as copying materials and keeping a file, it's a good idea to volunteer.
If you have no skills to help in such a situation, say something that shows concern for the other person like 遅くまで大変ですね。お疲れさまです。(It's been hard staying up late.Thank you for your hard work).

3.Overtime
残業
If you are a new employee and you may not know how things are going at work, you can do next things. Ask your boss if they have any other work to do like 何かやることがありますか？(Do you have anything to do?). Alternatively, it would be a good idea to ask, お先に失礼してもよろしいでしょうか？(Is it okay if I excuse you first?) before leaving the office.

4. What to do
業務
Before you leave work, check your work for the next day (prepare for a meeting, for example). Also, if you have plans to go out, etc., you should share your plans with other people. How to share information differs from company to company, so be sure to check the rules. Also, when you leave work, report to your boss and talk to your colleagues (especially, when the work is not finished).

What do you say before leaving work? Share in the comments!