You can respond to a tax notice by logging in to www.incometaxindiaefiling.gov.in.

Different types of notices can be found under options on the dashboard in your account.

Types of notices and how to respond to them

131(1A)
What is it for?
Assessing officer suspects you have concealed income.
How to respond
If you are unable to gather all the documents sought, send whatever you have within the deadline, along with an application seeking more time.

139(9)
What is it for?

Notice for defective return if wrong form is filled, or income details of a refund claim are missing, or there are multiple mistakes in filing.
How to respond
Respond within 15 days. Under ‘e-File’, select ‘e-File in response to Notice u/s 139(9)’ to proceed.

143(1)
What is it for?
Demand notice for additional tax or other required changes if there is a calculation error or incorrect information.
How to respond
Respond within 30 days. Find the notice under ‘e-Proceeding'.

148
What is it for?
For reassessment if some income has escaped assessment. A case up to six years can be reopened under this.
How to respond
File a return of the income being asked. Ask for a copy of the reasons for issuing the notice if you want to contest the notice.

156
What is it for?
Demand notice for due tax, interest, fine or penalty to be paid by the assessee.
How to respond
Pay dues within 30 days. Go to ‘e-File’ and then click on ‘Respond To Outstanding Demand’ to pay.