Advance tax filing deadline: late estimates void; tax notices required to secure advance tax collection. Assessees must file the statement/estimate under section 209A before the date the first instalment of advance tax is due; any statement filed after that date is void. For those who failed to file by 15th September 1978, notices under section 210 should be issued promptly, following review of registers per DOMS Circular No.31, so notices are dispatched before mid-November 1978 to avoid shortfalls in advance tax collection.