Estimate of advance tax: obligation to submit income and tax estimates and pay adjusted instalments accordingly. Section 212 establishes a mechanism for an assessee to submit an estimate of current income and the advance tax payable, to pay that amount in equal instalments or a single sum if only the last date remains, to submit revised estimates and to adjust any excess or deficiency in subsequent instalments; it also requires estimates to be sent in the prescribed form and verified in the prescribed manner.