For foreign residents who have a My Number card:

 The expiration date of the My Number card issued to foreign nationals (excluding permanent residents) is until the expiration of the period of stay on your residence card. If you do not complete the extension procedure for your My Number card by the expiration date of your period of stay, your My Number card will expire and you will be charged a fee (1,000 yen) to reissue it.

 However, if you apply for permission to renew your period of stay before the expiration date and you do not receive your new residence card by the time your My number card expires, you can extend the expiration date of the card for two months as a special case until you receive your new extended period of stay. Once you have received your new residence card with the updated period of stay, you will need to revisit the office and update the expiration date of your My Number card to match your new period of stay.

 Please note that the special two month extension cannot be made if the My Number card has already expired.