As per Explanation 2 to Section 139(1) of the Income Tax Act, 1961, the following classes of taxpayers are required to file their tax returns on or before October 31, 2024:

1. Corporate assessees.
2. Non-corporate assessees whose books of account are required to be audited under the Income Tax Act or any other law.
3. Partners of a firm whose accounts are required to be audited under the Income Tax Act or any other law.
4. The spouse of such a partner if Section 5A (Apportionment of Income between spouses governed by the Portuguese Civil Code) applies.

These categories of taxpayers typically have more complex financial situations that require audit and scrutiny, hence the extended deadline compared to individual taxpayers.