Sri Lanka, Sept. 14 -- Start with a managed demonetization and withdrawal of the Rs. 5,000 note, make it harder to hoard illicit cash, conduct anonymous transactions and keep money beyond the reach of the formal economy. Bring hidden cash into the banking system, widen the tax net, curb bribery and illicit transactions and strike at Sri Lanka's shadow economy. This is not an untested experiment. Our big brother India and several other countries have already travelled this road, giving Sri Lanka a tested international playbook and the lessons to phase out its highest-value note.

Sri Lanka stands at a rare inflection point. Having clawed its way back from the worst economic collapse in its post-independence history, the country is now und...