Profits Tax Return (BIR51) Filing Guide: Deadlines, Codes and Steps

The Profits Tax Return for corporations, Form BIR51, is issued in bulk on the first working day of April; about 270,000 profits tax returns went out on 1 April 2026. It is due one month after issue unless a tax representative's block extension applies. For the current 2025/26 cycle, those extended dates are 17 August 2026 for December year-ends (code D) and 16 November 2026 for January–March year-ends (code M). Loss-making M-code cases can apply to extend to 1 February 2027.

Last reviewed: September 2026 · Sources: IRD, Inland Revenue Ordinance (Cap. 112), GovHK press releases

Who receives a BIR51

The IRD issues BIR51 to corporations carrying on business in Hong Kong. Partnerships and other unincorporated businesses receive BIR52, the return for persons other than corporations, and sole proprietors generally report business profits on the individual tax return, BIR60. This guide concerns limited companies. Dormant companies and companies with no Hong Kong-sourced profit still receive a return, and still have to file it.

A newly incorporated company usually receives its first return about 18 months after incorporation. First-time returns (file-number prefix 23 or 97) may be filed within 3 months of issue, without applying for an extension. If a company is chargeable but has received no return, it must notify the IRD in writing within 4 months after the end of its basis period, under section 51(2) of the Ordinance.

The IRD's press release of 1 April 2026 confirmed that about 270,000 profits tax returns were issued that day, and that returns are generally due within one month of issue.

The 2025/26 timetable and block-extension codes

Most SMEs file through a tax representative, usually their accountant or auditor. Representatives receive a block extension from the IRD for their whole client list, and the extended due date depends on the company's accounting year-end. The dates below come from the IRD's Block Extension Scheme circular for 2025/26 returns.

A company with a 31 March 2026 year-end is therefore working towards 16 November 2026 right now. If it made an allowable loss, its representative can apply for the 1 February 2027 date. That list must reach the IRD by 2 November 2026, and individual cases are accepted exceptionally up to 16 November 2026.

Voluntary e-filing adds a month. If the return will be filed electronically through the Business Tax Portal, the representative can apply for a further one-month extension. The extra month runs from the day after the block-extension date, and the application must reach the IRD at least 7 working days before the return is otherwise due. The extension is void if the company then files on paper, and it opens the company to penalty action.

Beyond those dates, assume nothing. The circular says any further extension will be granted "only in the most exceptional circumstances". Requests must be made in writing at least 14 days before the extended date, with evidence. Telephone requests are refused outright.

What changes for the 2026/27 return

The return for the year of assessment 2026/27 will be issued around 1 April 2027. The IRD publishes a new block-extension circular each spring, and it has followed the same pattern in recent years: N returns due a month after issue, D returns in mid-August, M returns in mid-November, and M-code losses at the start of February. Expect the same shape in 2027, but take the exact dates from the new circular, not from this table.

What to file with the return

The return is only part of the submission. Corporations with gross income must attach supporting documents, set out in the BIR51 notes and instructions:

• the financial statements — statement of financial position, profit and loss account and the auditor's report;
• a tax computation showing how accounting profit becomes assessable profit, with supporting schedules;
• the relevant supplementary forms (S1 to S22), for example S1 for connected entities where the two-tiered rates are elected.

Every Hong Kong company must have its accounts audited, apart from dormant companies within section 5 of the Companies Ordinance (Cap. 622). Our note on the audit-exemption myth explains why the "small company" reporting exemption does not remove the audit.

The return itself asks for more than a profit figure. Among other things, it asks for the six-digit Hong Kong Standard Industrial Classification code for the principal business, and for amounts in Hong Kong dollars without cents. It also asks for disclosures on offshore claims, property profits, gains on capital assets, related-party fees, and the company's status under the global minimum tax rules. Assessable profits are reported before losses brought forward are deducted.

Filing on paper or online

Since 1 April 2023, supplementary forms must be filed electronically, in XML, whichever route the main return takes. That leaves three modes:

The IRD provides free tools for converting accounts to iXBRL. From 2025/26, electronic filing is compulsory for entities within Part 4AA of the Ordinance — broadly, members of multinational groups with annual revenue of at least €750 million — so for most SMEs it remains a choice. The extra month it earns is often the practical reason to choose it.

If a service provider files the return for you, the company must sign form IR1476, confirming the engagement.

Step by step: filing a BIR51

1. Check the return when it arrives. Confirm the file number, the year of assessment (2025/26 for returns issued in April 2026) and the accounting-date code your representative has on record.
2. Close the books for the basis period. For most companies the basis period is the financial year ending in the year of assessment. Reconcile every bank account and clear suspense items before the auditor arrives.
3. Complete the audit. The auditor's report must be signed before the return can be finalised, so book the audit well ahead of the due date.
4. Prepare the tax computation. Start from accounting profit, add back non-deductible items, deduct capital allowances, and exclude non-taxable income. Our deductible expenses checklist covers the add-backs.
5. Decide the two-tiered election. If the company has connected entities, agree which one elects and prepare form S1. The mechanics are in our guide to the 8.25% two-tiered rate.
6. Prepare the supplementary forms in XML and, if filing electronically, the iXBRL accounts and computation.
7. Have a director sign, and file by the due date: paper to the IRD, or electronically through the Business Tax Portal.
8. Diarise the assessment. The notice of assessment normally includes provisional tax for the following year, payable in two instalments. You have one month from the date of the notice to object to it in writing.

The return is only as fast as the close. JetFlow's finance module reconciles imported bank statements against the ledger and produces the P&L, balance sheet and trial balance your auditor asks for, while hot-folder OCR reads receipts straight into the books. See how JetFlow handles year-end preparation.

Paying the tax, and holding it over

Tax is payable according to the notice of assessment. Final tax for the year is reduced by provisional tax already paid, and provisional tax for the next year is added. If this year's profits are expected to be less than 90% of last year's, the company can apply to hold over provisional tax. The IRD's holdover FAQ sets the deadline as the later of 28 days before the due date or 14 days after the notice is issued.

Unpaid tax attracts a surcharge of 5%. A further 10% is added on the total unpaid, including the first surcharge, if it is still outstanding six months after the due date.

Penalties for filing late

Missing the due date without a reasonable excuse exposes the company to either of two routes, described in the IRD's penalty policy:

• Prosecution under section 80(2): a fine of up to HK$10,000, plus a further fine of up to three times the tax undercharged. The IRD can compound the offence instead of prosecuting.
• Additional tax under section 82A: an assessment of up to three times the tax undercharged. The company receives a written notice and has at least 21 days to make representations first.

In practice, a late return also brings an estimated assessment. The IRD raises one on the profit it thinks likely, and the company must lodge a written objection within one month of the notice, supported by the completed return and accounts, to have it corrected. The circular warns that taxpayers who persistently file late "are almost certain to face penalty action". Filing an incorrect return carries the same maximum penalties. Wilful evasion carries a fine of up to HK$50,000, three times the tax undercharged, and up to three years' imprisonment.

Common mistakes

• Treating the one-month date as a guideline. Without a representative and a block extension, the return is due one month after issue — 4 May 2026 this year.
• Asking for the e-filing month, then filing on paper. The extension is cancelled from the start, and the IRD may treat the return as late.
• Applying the loss-case extension to a profitable company. If the return later shows assessable profits, the same penalty exposure applies.
• Ignoring a return because the company is dormant or loss-making. Every return issued must be filed.
• Forgetting the XML supplementary forms. Supplementary forms, including S1 for a two-tiered election, cannot be filed on paper.
• Missing the objection window. An estimated assessment stands unless it is objected to in writing within one month of the notice.

Frequently asked questions

When is the profits tax return due in Hong Kong?

One month after it is issued, which for the April 2026 bulk issue meant 4 May 2026. Companies whose tax representative holds a block extension have later dates based on their year-end: 17 August 2026 for December year-ends and 16 November 2026 for January–March year-ends. Loss-making M-code cases can apply for 1 February 2027.

What do the N, D and M codes mean?

They are the IRD's accounting-date codes. N covers year-ends from 1 April to 30 November and gets no extension; D covers December year-ends; M covers year-ends from 1 January to 31 March. The codes determine the extended filing date under the block-extension scheme.

Do I need audited accounts to file a BIR51?

A corporation with gross income must submit its financial statements and auditor's report with the return. The only broad exception for Hong Kong companies is a dormant company under section 5 of the Companies Ordinance. A tax computation and schedules are also required.

Can I file my profits tax return online?

Yes, through the Business Tax Portal, with the accounts and tax computation in iXBRL. Supplementary forms must be filed in XML in every case. Voluntary e-filing entitles a represented company to a further one-month extension if applied for at least 7 working days before the due date.

What happens if I file my profits tax return late?

The IRD may issue an estimated assessment, and may prosecute under section 80(2) or impose additional tax under section 82A of up to three times the tax undercharged. Persistent late filers are singled out in IRD guidance as almost certain to face penalty action.

My company is new — when will I get my first return?

Usually about 18 months after incorporation. First-time returns can be filed within 3 months of issue. If you have chargeable profits and no return arrives, you must notify the IRD within 4 months after the end of the basis period.

Key takeaways

• BIR51 returns are issued on the first working day of April; about 270,000 profits tax returns went out on 1 April 2026.
• The base deadline is one month; block extensions run to 17 August (D) and 16 November (M), with 1 February 2027 for M-code losses.
• Voluntary e-filing earns a further month, but only on application and only if you actually e-file.
• File audited accounts, a tax computation and XML supplementary forms with the return.
• Late filing risks estimated assessments and penalties of up to three times the tax undercharged.

How long a BIR51 takes depends almost entirely on the state of the books when it arrives, and that is decided months earlier. Start free with JetFlow to keep the ledger audit-ready throughout the year.

This article is general information, not tax advice. Check your position with the IRD or a qualified tax adviser before acting.