The Swiss authorities online
If you lose your AHV card, or if your personal details change, apply for a new card.
Do not worry if you lose your OASI card. Your claim to pension benefits does not hinge on the card; you do not need show it to receive your pension. Your OASI number also appears on your health insurance card. If you lose your OASI card, and would like to replace it, contact your OASI compensation office to report the loss and to request a new card.
If you are living abroad, you need to contact the Swiss compensation office in Geneva to order an AHV card.