Assessee in default: failure to pay required advance tax instalments or to give required intimation triggers deemed default. A person is deemed to be an assessee in default if the person fails to pay on the specified date any instalment of advance tax required by an Assessing Officer's order; fails to send the prescribed intimation by the date an unpaid instalment becomes due; or fails to pay advance tax on the basis of the person's estimate of current income where such payment is required.