Moving to a corporation without retirement

Our company is in the form of a group of more than 10 companies.

Due to the operation of the company, four of them were decided to merge.

At this time, we would like to issue an announcement by simple movement, not by joining the company after retirement.

I just want to modify the legal employer.

For example, Company A and Company B merge.

If the number of people from Company B is merged into Company A, they are asking if it is possible to simply modify the corporation to Company A without retirement processing and hiring them.