NR income determination

When it applies. The Assessing Officer is of the opinion that the actual amount of income accruing or arising to a non-resident, directly or indirectly, through or from (a) any asset or source of income in India, (b) any property in India, or (c) any business connection in India, cannot be definitely ascertained.

How income may then be calculated (for assessment to income-tax)

1. at such percentage of the turnover so accruing or arising as the Assessing Officer considers reasonable; or
2. on an amount bearing the same proportion to the total profits and gains of the business (computed under the Act) as the receipts so accruing or arising bear to the total receipts of the business; or
3. in such other manner as the Assessing Officer may deem suitable.

Reading it in practice. The rule does not set a percentage; the first method leaves it to the Assessing Officer's reasonable judgment. The threshold is that the actual income cannot be definitely ascertained — it is not available merely because the books are inconvenient.