Hong Kong Profits Tax Supplementary Forms S1 to S18: Which One You Need and How to File

Supplementary Forms S1 to S18 for Hong Kong Profits Tax Returns

A profits tax return is rarely submitted alone. The IRD requires supplementary forms S1 to S18 with any BIR51, BIR52, or BIR54. The trigger is the nature of the business and the types of income or deductions claimed. These are mandatory annexures, not optional schedules. They break down specific categories of assessable profits or allowances. The IRD will reject a return if a required supplementary form is missing, incomplete, or inconsistent with the financial statements.

What Is Form S1 Hong Kong Profits Tax

Form S1 is the supplementary schedule for onshore manufacturing profits. A corporation carrying on a manufacturing business in Hong Kong uses S1 to compute the manufacturing profits and the apportionment between the concessionary and standard-rated portions. The concessionary rate is 8.25 per cent on half of the assessable profits in the qualifying class. The form requires total turnover, direct and indirect manufacturing costs, and the percentage of manufacturing activities performed inside Hong Kong. Without a completed S1, the IRD assessor will not accept the reduced rate and will default to the full 16.5 per cent rate on the entire assessable profits.

How to File Supplementary Form S18 Hong Kong

Form S18 is the schedule for concessionary profits from qualifying corporate treasury centres and qualifying treasury services. A Hong Kong corporation elected as a qualifying corporate treasury centre under section 14X of the Inland Revenue Ordinance (Cap. 112) files S18. It reports profits from intragroup financing, corporate treasury services, and related transactions with associated corporations. The form captures qualifying interest income and qualifying gains chargeable at the reduced rate of 8.25 per cent. Attach the election letter and a statement of connected entities. The IRD cannot process the concession without them.

Hong Kong IRD Supplementary Forms List

The table below lists each supplementary form S1 to S18 and the scenario that triggers its requirement. This list is current for the year of assessment 2025-26. Check the IRD forms index at ird.gov.hk for any revisions before filing.

Every form requires numerical breakdowns and supporting schedules. Some also require a statement from a connected entity or authorised officer. The IRD publishes the up-to-date forms as PDF files on its official website.

Offshore Claim and Form S3

A taxpayer relying on an offshore claim must file Form S3. The form lists total gross revenue, the amount claimed as offshore, and the basis of the claim. Examples include contracts negotiated and concluded outside Hong Kong, or services performed entirely abroad. The IRD examines the S3 with the tax computation and audited accounts. If the S3 is omitted or incomplete, the assessor will treat the entire turnover as taxable. The only remedy is a separate objection under the Inland Revenue Ordinance. Support the S3 with a detailed explanation of business operations. Where relevant, include documentary evidence: invoices, contracts and correspondence showing the place of performance.

Specified Forms and Electronic Filing via IXBRL

From the year of assessment 2025-26, the IRD introduced mandatory electronic filing of profits tax returns for in-scope multinational enterprise groups through the Business Tax Portal. Electronic filers must tag financial statements and tax computations in iXBRL format. The supplementary forms S1 to S18 are embedded in the iXBRL taxonomy. The filer selects the relevant schedules and populates the required data fields. Tax representatives use the Tax Representative Portal for electronic submission. The IRD intends to extend mandatory electronic filing to all entities by the year of assessment 2029-30.

Form S4 and Qualifying Debt Instruments

Form S4 is the schedule for profits from qualifying debt instruments under section 14A of the Inland Revenue Ordinance. A corporation holding a qualifying debt instrument issued by a Hong Kong resident lender or a recognised central clearing house reports interest income and disposal gains in S4. The form confirms the instrument meets the specified criteria. These include the minimum denomination and the requirement that proceeds finance infrastructure projects, transport undertakings, or other specified purposes. The IRD cross-checks the S4 against the certified true copy of the instrument.

Connected Entities and Related Party Transactions

Several supplementary forms require disclosure of transactions with connected entities. Form S10 captures service fees paid to or received from connected entities. Form S18 for corporate treasury centres requires a list of all connected entities participating in the treasury arrangement. The term "connected entity" takes its meaning from section 14X of the Inland Revenue Ordinance. The IRD may request a certified statement of the connected entity's name, address, place of incorporation and the nature of the relationship. Omitting a connected entity can result in disallowance of the concessionary treatment.

Block Extension and Return Date

A corporation filing within the block extension scheme must still submit the correct supplementary forms with the BIR51. The block extension does not exempt the taxpayer from attaching the required schedules. The return date printed on the BIR51 is the deadline. The IRD grants a block extension only for filing the return itself, not for preparing the supplementary schedules. If a supplementary form is not ready by the extended due date, file the return and completed schedules before the deadline anyway. Alternatively, request an individual extension in writing.

Where to Obtain the Latest Versions

The IRD maintains an official forms index at ird.gov.hk/eng/paf/bus.htm. It lists every supplementary form S1 to S18 alongside the profits tax returns BIR51, BIR52, BIR54 and property tax returns BIR57 and BIR58. Link to the IRD's own index rather than reproducing the forms. The department revises them periodically. A stale copy is worse than none. The IRD also provides electronic versions through the Business Tax Portal for iXBRL filers.