Advance tax obligations: assessees must file statements or estimates and pay instalments as computed under the statute. Section 209A requires assessees whose current income likely exceeds the specified threshold to file, in prescribed form and verified manner, either a statement of advance tax (if previously assessed) or an estimate of current income and advance tax (if not previously assessed), and to pay advance tax in equal instalments on dates under section 211; it permits substitution or revision of estimates, mandates fresh estimates and additional payments where estimated liability increases materially, allows limited extension in certain business cases, and defines current income for these purposes.