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Answers · Corporate income tax · YA 2026 · due 30 Nov 2026

Is there free software to do Form C-S for my Singapore company?

Yes. IRAS's own Basic Corporate Income Tax Calculator is an Excel file you download from iras.gov.sg with no login. It works out a trading company's tax computation and marks the Form C-S line number for each figure that goes in the return. You type those figures into myTax Portal yourself by 30 Nov 2026, for the financial year that ended in 2025. IRAS says a tax agent is not a requirement.

You need the year's accounts first, because the computation starts from the net profit in your financial statements. For Form C-S (Lite), a second IRAS file, the Record Keeping Assistant, works out the values from records you keep in it through the year.

Checked by hand against IRAS, read 29 Sep 2026 Edition YA-2027 · sources verified through 24 Jul 2026

Does your company file Form C-S?

Every company files a return each year, even with no income or a loss, unless IRAS has granted a waiver. A company incorporated in 2025 files nothing for Year of Assessment (YA) 2026 if it had not closed its first accounts in 2025, or closed them without starting business or receiving income: see a new company's first year.

It is Form C-S if the company:

  • is incorporated in Singapore;
  • has revenue of S$5,000,000 or below (its main income, not interest on the side);
  • earns only income taxed at the 17% rate, none of it at a lower rate or exempt under a tax incentive;
  • is not claiming carry-back of this year's capital allowances or losses, group relief, investment allowance, or foreign tax credit or tax deducted at source.

Fail any one and it files Form C. With revenue of S$200,000 or below it may file the shorter Form C-S (Lite), 6 fields instead of 18, but does not have to. A company that did no business and had no income files the Form for Dormant Company instead. A sole proprietorship or partnership is not a company. More on which form, and what goes in each box.

What do you need before you open any tool?

  • The year's financial statements, audited or unaudited, and a tax computation: the working that adjusts the accounting profit to the income IRAS taxes. For Form C-S you keep them rather than attach them, and send them if IRAS asks.
  • The records behind them, kept at least 5 years from the YA they relate to. IRAS says keeping only bank statements is poor record keeping. See what records to keep.
  • Corppass. Whoever submits must be authorised by the company in Corppass as an Approver for Corporate Tax (Filing and Applications). IRAS links step-by-step guides for setting that up. Have your Singpass and the company's Unique Entity Number (UEN) ready.

How do you do Form C-S yourself with IRAS's tools?

  1. Download the calculator. On IRAS's Calculators page, choose "BTC for Companies Filing Form C-S" for the YA you are filing. IRAS made it for trading companies. Don't use it for an investment holding company (one that mainly holds property or shares for rent, dividends or interest; IRAS has a separate template for these), a claim for industrial building or land intensification allowance, or accounts kept in a currency other than Singapore dollars.
  2. Open it in Excel on a computer. Its buttons, such as Enter for each new asset, run macros, which Excel for the web cannot run. Excel on Windows blocks macros in a file from the internet: right-click the saved file, choose Properties, tick Unblock, then open it. No desktop Excel? Filing on myTax Portal is still free: work the figures out by hand with IRAS's guide to preparing a tax computation, then type them in.
  3. Fill the yellow boxes. Start from the net profit or loss before tax in your financial statements, with last year's tax computation and Notices of Assessment beside you if the company has filed before. A column gives the Form C-S line number, and the Form C-S (Lite) one, for each figure that goes in the return. IRAS says it gives estimates and may not cover every case.
  4. Open the return. At mytax.iras.gov.sg, open the File Form C-S/C digital service and set aside at least 10 minutes. If you enter revenue of S$200,000 or below, the portal offers Form C-S (Lite). Check the unused capital allowances, losses and donations from earlier years, which the portal fills in, against your records.
  5. Type the figures in. After 15 minutes idle the portal gives you 2 minutes to respond, then logs you out, so press Save Draft if you stop. A saved draft is kept at least until 30 Nov.
  6. Submit. Only an Approver submits. A Preparer can complete the return and pass it on, but IRAS sends the Approver no alert, so tell them. The acknowledgement is instant.

Filing Form C-S (Lite)? IRAS's Record Keeping Assistant, on the same Calculators page, is an Excel file you keep through the financial year. Record income and expenses in it as they happen, and its green boxes give the values to type into Form C-S (Lite). IRAS says it is for straightforward tax calculations, and rules out the same three cases as the calculator, plus a GST-registered company.

IRAS has a step-by-step user guide (PDF) and a video, "Filing your Form C-S on myTax Portal" (6 min 50 s). The portal steps in order, with a worked example: filing Form C-S on myTax Portal, step by step.

Can software file Form C-S for you?

Yes, if you keep your books in it. Under IRAS's #SeamlessFilingFromSoftware (#SFFS), accounting software prepares Form C-S from your books, and your Corppass Approver reviews it and files it to IRAS from inside the software. You map your chart of accounts once.

It is only for companies that qualify for Form C-S, keep Singapore dollars as their functional currency, are not an investment holding company or a service company serving only related parties, and have no subsidiaries, associates, joint ventures or investment in intangibles.

The software comes from its developers, not from IRAS, so ask them what it costs. IRAS points to its ASR+ listing for such software. It says it has only tested how that software connects to IRAS, and that it is rebranding the listing.

For YA 2023 to YA 2027, a Form C-S filed through accounting software is due 15 Dec instead of 30 Nov. A return you type into myTax Portal is still due 30 Nov.

When is it due, and what does late cost?

30 Nov every year: for YA 2026, 30 Nov 2026. The Estimated Chargeable Income (ECI) is a separate return, and your ACRA Annual Return does not replace Form C-S.

File late and IRAS may issue an estimated Notice of Assessment, which can assume your income went up and must be paid within 1 month.

Instead of prosecuting, IRAS may offer to let the company pay up to S$5,000 per offence (a composition amount), and the company must still file the overdue return. If the return or that payment is not in by its due date, IRAS can summon the company and its directors to court, and a conviction carries a fine of up to S$5,000 per offence. With 2 or more years unfiled, the company can also be ordered to pay a penalty of twice the tax assessed.

Do it in Simpler Tax

Is there a free app that keeps the books and works out the figures?

Yes. Simpler Tax is a free desktop app for Windows 10 and 11, for Singapore private limited companies: no account, no email, no trial. It keeps the company's books in one file on your own computer, from PDF invoices and receipts, receipt photos, bank statement CSV files, spreadsheets and InvoiceNow files. It checks every document by adding it up: what adds up is recorded, and what doesn't becomes one question for you.

For Form C-S it works out the full computation from those books, with a copy button on every box it computes. You fill the form's financial statement section from the statements themselves. You type the figures into myTax Portal and sign with your own Corppass. It files nothing, so your due date stays 30 Nov.

Download for Windows Simpler-Tax_1.0.0_x64-setup.exe · 55 MB · not signed yet · free · SHA-256 on the home page

Questions people ask

Do I need a tax agent to file Form C-S?

No. IRAS says it is not a requirement. Directors stay responsible for filing on time and correctly, even when a tax agent is engaged.

Does Simpler Tax file Form C-S for me?

No. It prepares the figures; you type them into myTax Portal and sign with your own Corppass. It holds no Corppass credentials and has no route to myTax Portal.

Sources

Statutory figures on this page are read from the Simpler Tax rulebook at build time, edition YA-2027, every source last checked 24 Jul 2026. The rulebook entries named below are the ones this page was computed from; the IRAS pages are what they were verified against.