健康保険限度額適用認定証 (Certificate of application of health insurance limit) - the first time I encountered this term because of my wife getting hospitalized. From its definition, it limits the amount that you have to pay to the hospital when you or a family member gets hospitalized.
The process differs depending on the insurance one holds. For our case, our company administrator applied this for us and we received a 'hagaki' (or postcard). This is what we need to give to the hospital during or after payment.
This time, we are submitting it to the hospital after payment. And any amount we paid exceeding a certain amount will be refunded to us.
Thanks be to God for such financial assistance.