New Delhi, June 26 -- Under-invoiced exports and over-invoiced imports, with the difference stashed away abroad in collusion with allied agents, were once a classic way for resident Indians to jump capital controls that kept them from sending wealth overseas.

Once India's economy opened up, round-tripping games began, with local money sneaking out only to return, often aimed at exploiting a special edge foreign investors had. Closing incentives for this has been a reform goal, but at times, the vigil must heighten.

This week, non-residents had a 'wow' moment, as a sample of social media suggests, upon learning how they could help India hoover up dollars.

Roughly, since $1 million can be leveraged up to nine times-via a loop of loans av...