Hong Kong Mandates Electronic Filing for Pillar Two Top-Up Tax Starting January 2026

Inland Revenue Department confirmed that Pillar Two top-up tax filings in Hong Kong will be mandatory via an electronic portal from January 2026. In-scope Part 4AA entities must submit notifications and returns through the new Pillar Two Portal, accessed via the Business Tax Portal (BTP), using an organisational e-cert with AEOI functions. While Pillar Two applies to fiscal years starting 1 January 2025, mandatory e-filing begins in 2026, with the first notification due in 2026 and the first return in 2027 for calendar-year taxpayers.

Under the new framework, Part 4AA entities that are members of in-scope multinational enterprise (MNE) groups will be required to submit top-up tax notifications and top-up tax returns electronically using a system designated by the Commissioner.

Pillar Two Portal rollout

To support compliance, the IRD is developing a dedicated Pillar Two Portal, which will be launched in phases starting from January 2026. The portal is an extension of the existing Business Tax Portal (BTP).

Entities subject to Pillar Two will be required to:

• Register a Business Tax Portal (BTP) business account
• Access the Pillar Two Portal through the BTP
• Submit filings exclusively via the electronic system

Authorisation and authentication requirements

Filings must be submitted by an authorized individual using an e-cert (organizational) with AEOI (Automatic Exchange of Information) functions enabled. Personal or non-organizational credentials will not be sufficient.

Electronic tax assessments

Following submission and assessment, electronic notices of top-up tax assessment will be issued directly to the relevant entities’ BTP business accounts, where they can be viewed and downloaded.

Effective timeline

While the Pillar Two rules apply to fiscal years beginning on or after 1 January 2025, the mandatory electronic filing obligation becomes operational with the launch of the Pillar Two Portal in 2026. For calendar-year taxpayers, the first top-up tax notification is expected to be due in 2026, followed by the first top-up tax return in 2027, in line with standard Pillar Two filing timelines.