781. Allowable losses.

Except as otherwise expressly provided:


    (1)     the amount of a loss accruing on the disposal of an asset is computed in the same way as the amount of a gain accruing on a disposal is computed1;


    (2)     the statutory provisions which distinguish gains which are chargeable gains2 from those which are not, or which make part of a gain a chargeable gain, and part not, apply also to distinguish losses which are allowable losses from those which are not, and to make part of a loss an allowable loss, and part not3; and references to an allowable loss must