If a Musi was the sole (100%) owner of a house, had paid the applicable Hissa Jaidad on it, and had obtained the certificate of Jaidad, would the surviving spouse and children (if they are Musis) be required to pay Hissa Jaidad on the same house after inheriting it?

Yes. Upon the Musi’s demise, the shares of the house inherited by the surviving spouse and children become their respective properties. Hissa Jaidad accordingly becomes payable on the share inherited by each Musi at their prescribed Wasiyyat rate.

For example, if the surviving spouse inherits one-eighth (1/8) of the house, they will be required to pay Hissa Jaidad on one-eighth of the assessed market value of the house, calculated at their applicable Wasiyyat rate.