How to deal with health insurance and taxes when working two jobs?

I’m currently a full-time permanent employee at company A, and they pay my health insurance, taxes and everything.

As the job is very lax, I’m considering joining company B also as a full-time employee, while continuing at A. This company also provides health insurance and such.

As I don’t want company A to find about B (and if possible B about A), what’s the best way to deal with taxes and health insurance? Anything else to keep in mind when double working?

4 comments
  1. Sounds difficult without B knowing since if you enter as 正社員 they will require paperwork that you need to get from the previous company.

    If B knows however you could ask them to have an independent contractor style of relationship, where you effectively invoice your salary from them, and do your tax adjustment at the end of the year. That should leave A in the dark.

    That said, many companies have explicit rules that don’t let you take on a second job (even a baito) without prior written authorization. So tread carefully.

  2. Technically you can be employed by multiple companies, but legally you can only register one company that provides social insurance (aka the main company). Some companies will definitely reject you outright if you’re being employed as 正社員 by A and want to be employed as 正社員 again by B.

    You better off trying to approach this a side job (副業) explicitly. Most companies these days allow side job, so maybe company A allows them. That should be a more safer approach regarding tax and the implications. Company B would love them too.

  3. Technically, very hard.

    First, withholding of the residence tax is calculated based on the total income, but only one company is obliged to withhold the tax. If the company notices that your withholding amount requested by the city doesn’t match the amount they pay you , they can come to know that you have other incomes.

    Second, when you work at two companies, you need to pick one of them as primary for shakai hoken and tell that to the shaho office. They will send the notice to both companies.

  4. this was already asked.. you can only if both companies agree. One is chosen as the main one. Otherwise you can’t and both companies will find out so you might get fired from both.

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