Year-wise Archives of Circulars, Instructions, Notifications, Orders, Press Releases, etc. updates issued by various Regulators, like CBDT, CBIC, MCA, SEBI, etc.):

CBDT Updates (Income Tax)
For downloading various Income Tax Circulars, Instructions, Notifications, Orders, Press Releases, etc. issued by the Central Board of Direct Taxes (CBDT) in different years, please refer the following links:
CBDT Circulars: 2020, 2019, 2018, 2017
CBDT Instructions: 2020, 2019, 2018
CBDT Notifications: 2020, 2019, 2018, 2017
CBDT Orders: 2020, 2019, 2018, 2017
CBDT Press Releases: 2020, 2019, 2018
Note: For Official/ updated copy of relevant Circulars/ Instructions/ Notifications/ Orders, please visit the Income Tax Deptt. website.
CBIC Updates (GST)
For downloading various GST Circulars/ Notifications/ Orders issued by the Central Board of Indirect Taxes & Customs (CBIC) under various GST  Acts/ Rules, in different years, please refer the following links:
CBIC Circulars (CGST/ IGST/ UTGST): 2020201920182017
CBIC Central Tax (CGST) Notifications: 2020201920182017
CBIC Central Tax Rate (CGST Rate) Notifications: 2020, 2019, 2018, 2017
CBIC Integrated Tax (IGST) Notifications: 2020201920182017
CBIC Integrated Tax Rate (IGST Rate) Notifications: 2020, 2019, 2018, 2017
CBIC UT Tax (UTGST) Notifications: 2020201920182017
CBIC UT Tax Rate (UTGST Rate) Notifications: 2020, 2019, 2018, 2017
CBIC Compensation Cess Notifications: 2020201920182017
CBIC Compensation Cess Rate Notifications: 2020201920182017
CBIC Orders (CGST/ IGST/ UTGST): 2020, 2019, 2018, 2017
CBIC Press Releases: 2020, 2019, 2018, 2017
Note: For Official/ updated copy of the relevant GST Circulars/ Notifications/ Orders, please visit the CBIC website.
MCA Updates (Company Law)
For downloading various General Circulars/ Notifications/ Orders issued by MCA under the Companies Act/ Rules and other allied Corporate Laws, in different years, please refer the following links:
MCA General Circulars: 2020, 2019, 2018, 2017, 2016
MCA Notifications: 2020, 2019, 2018, 2017, 2016, 2015
MCA Orders: 2020, 2019, 2018, 2017, 2016, 2015
Note: For Official/ updated copy of relevant General Circulars/ Notifications/ Orders, please visit the MCA website.
SEBI Updates (Investors' Protection)
For downloading various Circulars, Instructions, Notifications, Orders, Press Releases, etc. issued by the Securities & Exchange Board of India (SEBI) in different years, please refer the following links:
SEBI Circulars: 20202019
SEBI Press Releases: 2020