I can't find any information on Google, so I thought maybe some folks could help me here.

I am resident in Japan and my company provides me national insurance.
I also have a private insurance on the side (and my company knows about it).

In my home country, it is pretty common to have both: national insurance covers part of the fee, the private one covers the rest.

I have been doing the same here:
- I go to the doctor
- hand my national insurance card
- pay the fee (30% of the full price because the national insurance covers about 70%)
- ask the clinic to provide a bill and to stamp my private insurance form to claim refund
- submit the docs to my private insurance
- get refunded

I did that in more that 5 different clinics during the last two years.

But last week, I went to see a new doctor (non-Japanese) that told me that was illegal to do so: it is either the national insurance covers 70% and I pay the rest OR I don't use national insurance and use my personal insurance for all the fee.

I am very surprised as it doesn't make sense at all to me.

Do you know if the doctor is right?

Thank you