Tax clearance requirement: departure barred unless employer or payer furnishes undertaking and PAN or certificate is produced. Section 420 conditions departure on a tax clearance mechanism: non domiciled persons in India for business, profession or employment with Indian income must produce a prescribed undertaking from the employer or payer accepting tax liability for issuance of a no objection certificate; departing domiciliaries must furnish PAN, travel purpose and estimated period or a prescribed certificate. Authorities may require certificates where liabilities exist, subject to recorded reasons and senior approval; owners or charterers allowing departures without certificates incur recoverable liability and are deemed assessees in default.