If the fixed assets which have been completely depreciated are destroyed or become obsolete at the expiration of their useful years, the difference, if any, of the residual value previously estimated over the proceeds from sale of scraps may be charged to loss for the current year. In case the proceeds from sale of scraps exceed the residual value previously estimated, the difference shall be charged to income of the current year.
Where the fixed assets are destroyed or become obsolete on account of specific reasons, at any time before the end of their prescribed service years, their undepreciated value may, upon submission of reliable documentary evidence, be charged to loss for the proper fiscal year, provided, that proceeds from the sale of scraps, if any, shall be considered as income.