The income-tax (I-T) department has identified about 400,000 taxpayers who will face scrutiny under the new faceless assessment scheme. Notices were being served to a little over 100,000 assesses, seeking explanation on the returns filed within 15 days, said an official privy to the development. However, about 10,000 such letters were undelivered and, in some cases, bounced back. The deadline of sending scrutiny letters ends on September 30. The tax department is learnt to have finalised computer-assisted scrutiny selection (CASS) cycle for the current year and has selected about 100 parameters to scrutinise returns under the new system.