An assessee would receive intimation under Section 143(1) if the assessee has paid either more or less than the amount which he is actually liable to pay. In case of payment made less than the actual amount, the assessee need to make the payment and resolve the issue. In case of payment made more than the actual amount, he will be informed about the refund amount by intimation.

This intimation notice is sent by the Income Tax Department with intent of obtaining documents, books of Accounts or any written information for scrutinizing the records and the return filed by the assessee.

This notice is sent by Assessing Officer in case of a defective return. If the Assessing Officer feels that the Income Tax return filed by an assessee is defective and needs certain rectification, then he can send a notice under Section 139(9)

This intimation is sent by the Income Tax Department to inform the assessee that his request for Income Tax Return will now be sent for detailed scrutiny. This intimation is usually sent after sending Notice under Section 142(1). It means that the Assessing Officer has not received any relevant documents or is not satisfied with the obtained documents.

This is also known as Notice of Demand which is served to an assessee with instruction for payment of any tax, interest or penalty.