Form BIR51 Profits Tax Return Hong Kong Corporations: Filing Guide and Deadlines

Filing the Form BIR51 Profits Tax Return Hong Kong Corporations

Form BIR51 is the profits tax return the Inland Revenue Department (IRD) issues to every Hong Kong corporation on its active case list. The IRD posts the Form BIR51 profits tax return Hong Kong corporations receive on the first working day of April each year. It covers the year of assessment that ended on 31 December of the previous calendar year. The return requires the corporation to declare its assessable profits or adjusted loss for the relevant accounting period and to compute the profits tax payable under the Inland Revenue Ordinance (Cap. 112).

Hong Kong Profits Tax Return Filing

The hong kong profits tax return filing process starts when the IRD issues Form BIR51 to the corporation's registered office address. Complete the return, attach the required supporting documents, and deliver everything back to the IRD by the due date stated on the return. Supporting documents include audited financial statements (or certified accounts if the corporation is exempt from audit), a tax computation showing how the assessable profits or adjusted loss is derived from the accounting profit, and any supplementary forms (S1 to S18) that apply.

The IRD uses the information on the return to raise a profits tax assessment. If the corporation disagrees with the assessment, it may object within one month of the date of the assessment notice.

BIR51 Deadline Hong Kong

The BIR51 deadline hong kong is one month from the date of issue printed on the return. The IRD issues most BIR51 returns on the first working day of April. The standard deadline is therefore the first working day of May.

Most corporations rely on the block extension scheme. Under this scheme, the IRD automatically extends the filing deadline for corporations whose accounting date falls on a common year-end date. For a 31 December accounting date, the extended deadline is 15 August of the same year. For a 31 March accounting date, the extended deadline is 15 November of the same year. Corporations with other accounting dates must apply for a non-standard extension in writing.

The block extension scheme applies only if the corporation files its return through a tax representative, a certified public accountant or solicitor. A corporation filing without a tax representative faces the original one-month deadline. Late filing attracts penalties under the Inland Revenue Ordinance. The IRD may impose a late filing surcharge, issue an estimated assessment, or prosecute persistent defaulters.

Corporation Tax Return Hong Kong

The corporation tax return hong kong is the same document as Form BIR51. The IRD uses the term "Profits Tax Return - Corporations" on the form itself. The return covers all sources of income chargeable to profits tax under section 14 of Cap. 112: trading profits, interest, royalties, and rental income from Hong Kong property.

A corporation with no assessable profits for the year must still file the return. The IRD does not accept silence as a nil return. State the adjusted loss or nil profit on the form and attach the audited accounts and tax computation.

Supplementary Forms S1 to S18

The IRD requires a corporation to attach one or more supplementary forms to its BIR51 return if the corporation claims certain deductions or falls into specific categories. The supplementary forms are:

• S1: Depreciation allowances
• S2: Industrial building allowances
• S3: Commercial building allowances
• S4: Losses set-off
• S5: Group relief
• S6: Offshore claim (non-Hong Kong sourced income)
• S7: Foreign tax credit
• S8: Interest deduction
• S9: Research and development expenditure
• S10: Technical education expenditure
• S11: Environmental protection expenditure
• S12: Donations to approved charities
• S13: Concessionary tax rate (for qualifying treasury centres, aircraft leasing, etc.)
• S14: Elective single entity tax treatment for group financing
• S15: Tax reserve certificates
• S16: Provisional tax offset
• S17: Two-tiered profits tax rates
• S18: Tax exemption for qualifying funds

The most commonly filed supplementary forms are S1 (depreciation allowances), S4 (losses set-off), S6 (offshore claim), and S17 (two-tiered rates). A corporation making an offshore claim must also refer to Departmental Interpretation and Practice Note No. 21 (DIPN 21) for the IRD's interpretation of the source of profits.

Electronic Filing and the Business Tax Portal

The IRD is moving towards mandatory electronic filing of profits tax returns. From the year of assessment 2025-26, mandatory electronic filing applies to relevant entities of in-scope multinational enterprise groups. These entities must file through the Business Tax Portal or the Tax Representative Portal and tag their financial statements and tax computations in iXBRL format.

For all other corporations, electronic filing is voluntary but encouraged. The IRD has stated an intention to reach full electronic filing by 2030. Electronic filers benefit from a longer filing window under the block extension scheme and receive instant confirmation of receipt. To file electronically, the corporation or its tax representative must register for a user account on the Business Tax Portal. The portal accepts the BIR51 return, supplementary forms, audited accounts, and tax computation in iXBRL. Paper filing remains available for corporations not subject to the mandatory e-filing requirement.

Provisional Tax and the Return

Form BIR51 also deals with provisional tax. When the IRD issues a profits tax assessment based on the return, it also imposes provisional tax for the following year of assessment. The provisional tax is calculated by reference to the assessable profits of the current year. The corporation may apply to holdover provisional tax if it expects its profits for the following year to be lower than the current year's profits.

The BIR51 return includes a section where the corporation can indicate whether it intends to apply for a holdover of provisional tax. The application must be made in writing within 28 days before the due date for payment of the provisional tax.

What the IRD Expects

The IRD expects every corporation to file its BIR51 return on time, with complete and accurate information. The return must be signed by a director, the company secretary, or a tax representative authorised in writing. Retain copies of the filed return and supporting documents for at least seven years.

If the corporation has ceased business or is dormant, it should still file the return until the IRD confirms that no further returns are required. A corporation that has been struck off the Companies Register is not required to file, but the directors should ensure that the company's tax affairs are finalised before applying for deregistration.

Where to Find the Form

The IRD publishes Form BIR51 and all supplementary forms on its website at https://www.ird.gov.hk/eng/paf/bus.htm. The current version of the form, explanatory notes, and the list of supplementary forms are all available there. The IRD revises the form periodically. Download the latest version rather than reusing a previous year's copy.