Let’s understand the query- 
An individual taxpayer has been regularly filing ITR every year, and tax audit reports have also been filed. Recently, the assessee received a notice from the Income Tax Department under Section 131(1A) asking for submission of books of accounts and documents for the past four years. Now assessee want to know: What is the purpose of issuing a notice under Section 131(1A)? Is this notice related to scrutiny assessment, survey, or some other proceeding? What is the procedure after such a notice is issued and received by the assessee?
Answer- 
 
1. Purpose of issuing a notice under Section 131(1A)
Section 131(1A) gives wide investigation powers to the Income Tax Department.
A notice under this section is issued when the authority has “reason to suspect” that:

• The assessee is concealing income, or
• The assessee is likely to conceal income, and
• The department considers it necessary to call for books of accounts, documents, statements, or evidence.

Key points:

• It is an investigation/enquiry power, not an assessment notice.
• It can be issued even if no assessment, no scrutiny, and no proceeding is pending.
• It is often used when the department has received information from third-party sources, data analytics, risk flags, FIU inputs, TDS/TCS mismatches, or survey/reconnaissance inputs.

2. Is this notice related to scrutiny assessment, survey, or something else?
A Section 131(1A) notice is not a scrutiny notice under Section 143(2).
Instead, it is generally connected to:
A. Pre-survey investigation
131(1A) is explicitly empowered for use before or during a survey under Section 133A.
Assessing Officers, Investigation Wing, and other authorised officers use it to collect information before deciding whether a survey or further action is required.
B. Independent investigation
The notice can also be used independently, even when no survey is intended.
It simply means the department wants deeper verification of past records.
C. It is NOT a tax audit verification or routine compliance notice
Even though the assessee is regularly filing ITR and Tax Audit Report, 131(1A) notice is triggered only when there is specific information or suspicion.
So, this notice is not scrutiny assessment, but it may lead to one if discrepancies are found.

3. What happens after such a notice (procedure)
Step 1: Assessee must furnish books/documents
You are required to submit:

• Books of accounts,
• Ledgers, vouchers, supporting documents,
• Bank statements, invoices, agreements, etc.,
  for the years specified in the notice (past four years in your case).

Submission may be online or physically, as specified.
Step 2: Personal appearance (if required)
The department may ask the assessee to:

• Appear personally,
• Give sworn statements,
• Explain transactions, entries, or sources of income.

This power is similar to civil court powers.
Step 3: Department reviews information
Based on the documents/statements, the department may:

• Close the enquiry if everything is satisfactory, or
• Issue a notice under Section 148 (reassessment) if income escapement is found, or
• Convert the case into a scrutiny assessment under Section 143(2)/142(1), or
• Proceed with a survey under Section 133A, if warranted.

Step 4: Outcome
If explanations and records are proper, the matter usually ends without further adverse action.

Summary for your situation

• Purpose: Investigation based on suspicion of possible concealment (not routine).
• Nature: Not scrutiny; it is a preliminary investigation or pre-survey enquiry.
• Procedure: Submit documents → give explanations if asked → department decides next steps.