- Simpler Tax
- Filing Form C-S on myTax Portal
Filing Form C-S on myTax Portal, step by step, with the pack beside it
Form C-S is filed online only, at myTax Portal, by someone the company has authorised in Corppass for the Corporate Tax (Filing and Applications) digital service, and it is due on 30 Nov 2026 for YA 2026. You tick the four Part A declarations, type the Part B lines 1 to 20, let the portal compute the tax, add the Part C figures from the financial statements, and an Approver submits.
Simpler Tax's Form C-S pack sits beside the portal with a Copy button on every line: the 21 Part B lines you type, 5 the portal computes for you to check, and the 3 it carries into next year. It files nothing.
Checked by hand against the app and the IRAS filing FAQ Edition YA-2027 · sources verified through 24 Jul 2026
Before you start: Corppass
The person filing must be authorised in Corppass for IRAS's Corporate Tax (Filing and Applications) digital service. That can be an employee or a tax agent. Corppass has two roles that matter here: an Approver can complete, approve and submit the return to IRAS; a Preparer can complete it and pass it to an Approver, and no further. A company needs at least one Approver to file at all.
There is no paper form. E-filing has been the only route since YA 2020. See which of the three returns you file, and what goes in each box.
What the pack shows
On the Tax screen the Form C-S pack is titled Simplified Corporate Income Tax Return. Its cover reads: the tax computation, line by line, in IRAS's own BTC numbering; open myTax Portal beside this window and work down the list, each line ticks off as you copy it, so you can stop mid-way and pick up where you left. Under the cover come, in order:
- Part A · Declarations: the four conditions, checked against the books where the books can answer.
- The computation, line by line, lines 1 to 9: from the net profit in the accounts to the adjusted profit before capital allowances.
- Deductions, other income, chargeable income, lines 10 to 20: capital allowances, losses brought forward, separate-source income, donations, and line 20, the chargeable income before the exempt amount.
- Carried forward, lines 21 to 23: the carry register, what the close carries into next year. Not a portal box.
- What the portal computes for you: the exempt amount, the tax, the rebate and the net tax, each with the figure to expect.
Every line has one Copy button and a tick. Every subtotal shows its own arithmetic under it, re-added in front of you, with a tick only when it lands. Above the lines a bar counts how many of the 29 lines are copied and how many are ready, says where to resume, and reminds you: Press C to copy the next line. At the foot are I have filed this, Copy all lines (the 24 lines as tab-separated text: line number, label, figure) and Close YA2026 →.
The pack refuses rather than guesses. A question about the books that nobody has answered is a refusal: the pack shows the reason and the fix in the engine's words and no lines at all, the head chip reads flagged, and the desk card reads Not issued. A year whose basis period has not ended is not put to you as a refusal: the card reads waiting, with no lines, and says the return exists once the year has passed. A document still in Review leaves the lines on the pack, marked provisional, with a plate saying every figure moves until that queue is empty. A filing you have recorded whose books then moved keeps every line, reads flagged, and carries a plate headed The books behind this filing have moved.
The steps
Eight steps, in the order the portal asks. Where this page names a portal screen it is from IRAS's own filing FAQ or its explanatory notes; the portal shows its own labels, and IRAS redesigns it, so read the box's label before you paste.
- Open the pack and the portal side by side. In Simpler Tax open the Tax screen. The card marked Form C-S, titled Simplified Corporate Income Tax Return, shows the return currently due with its due date, 30 Nov 2026 for YA 2026. The chip at its head reads waiting when the figures are settled and the return is not yet filed, provisional while something in the books still moves, verified once you have recorded the filing, and flagged in two cases: the engine refused to issue the pack, in which case there are no lines to copy and the desk card reads Not issued; or the books moved after you recorded the filing, in which case every line is still there and a plate headed The books behind this filing have moved says so. A year whose basis period is still running is not shown as a refusal: its card reads waiting with no lines, and one line says the return exists once the year has ended. The net tax line at the bottom carries the engine's own verdict: agreed means every figure traced to the ledger. Copy nothing until the head chip reads waiting and the net tax line reads agreed. In a browser, sign in to myTax Portal with Corppass and open the File Form C-S/C digital service. IRAS's FAQ says the portal ends a session after 15 minutes without activity, with a 2-minute warning, so keep moving or save the draft.
- Part A: tick the declarations. The pack's Part A · Declarations block lists the four Form C-S conditions and checks the ones the books can answer. There is nothing to copy here; the portal asks for the same four as tick-boxes. The portal also asks who reviewed the return and which financial period it covers. The pack does not carry those two; you type them.
- Part B: copy lines 1 to 20, one at a time. Work down the pack's first two groups, The computation, line by line and Deductions, other income, chargeable income: 21 lines, items 1 to 20 with item 19 on two lines. Each line has one Copy button at its right. Press it, and the figure lands on the clipboard as a bare number with two decimals, no currency sign and no thousands separator; paste it into the portal's box for the same item number. The portal's wording may differ from the pack's label, so read both before you paste. The line ticks off, the counter at the top of the pack moves from 0 of 29 copied, and the next line is marked Next. Pressing C on the keyboard copies the next line without reaching for the mouse. A line at 0.00 still has its Copy button and counts in the bar.
- Lines 21 to 23: the carry register, not a portal box. The pack's third group, Carried forward, is the unutilised capital allowances, losses and donations that this year could not absorb, the figures Close YA2026 carries into YA 2027's opening. For the worked company the pack prints line 21 0.00, line 22 0.00, line 23 0.00: it had a profit, so nothing is left over. The three lines have Copy buttons and count in the bar like every other, but IRAS's Part B ends at item 20 and the repo records no Form C-S box for them, so there is nothing to type from them. The portal's own items 21 to 23 are not the pack's.
- Check what the portal computes for you. After line 20 there is nothing more to type in Part B. The exempt amount, the tax at 17%, the rebate and the net tax are the portal's own arithmetic. The pack's last group, What the portal computes for you, shows the figure to expect on each, and under the net tax it says: check it shows that figure before you press submit. If the portal shows a different figure, one of the lines above it was typed wrong; the pack's arithmetic under each subtotal tells you which.
- Part C: the figures from the financial statements. The portal's Part C asks for figures copied from the accounts: revenue, gross profit, directors' remuneration, total remuneration, medical, transport and entertainment expenses, inventories, trade receivables, and a few yes-or-no declarations. The pack does not carry them. They come from the same books, but you take them from the financial statements, not from this pack.
- Submit, or hand it to the Approver. Only you can file it. A Corppass Approver submits the return to IRAS. A Preparer can complete it and pass it to an Approver, and IRAS's FAQ says the Approver is not alerted automatically, so tell them. A saved draft stays in the portal for 21 days or until 30 Nov 2026, whichever is later.
- Record it in Simpler Tax. Back on the pack, the foot reads Mark Form C-S as filed and says: Only you can file it. Submit in myTax Portal, then record it here; this is what stamps the pin on your year map, and the year cannot close before it. Press I have filed this. The filed mark has an Undo button. One thing the foot does not say: the close button checks the pack, not the filing. It refuses only a year the pack refuses, so nothing in the app stops Close YA2026 → before I have filed this; keep the order yourself. The close carries lines 21 to 23 into YA 2027's opening and has no undo button, it writes the register the next year opens from, so press it once the return is in and not before.
Part A on the pack
The pack's Part A block says: tick-boxes in the portal, checked here against your own books, nothing to type. The four rows, for the worked company:
| No. | Declaration | What the pack shows |
|---|---|---|
| 1 | The company is incorporated in Singapore. | Your declaration; the pack prints the incorporation date from Settings beside it. |
| 2 | Annual revenue is S$5,000,000 or below. | Checked against the posted books: the worked company's S$800,000.00 is under the cap, so the row shows a tick. |
| 3 | All income is taxable at the prevailing 17% rate. | The pack computed at 17%, so the row shows a tick. |
| 4 | No claim for carry-back of this year's capital allowances or losses, group relief, investment allowance, foreign tax credit or tax deducted at source. | None in the pack, so the row shows a tick. |
A company whose revenue is S$200,000 or below gets one more line in this block, saying it may file Form C-S (Lite) instead, in 6 essential fields. Filing Lite is optional; the pack's figures serve either form.
A worked pack for YA 2026
The same company as the Form C-S page: S$800,000.00 of sales, S$120,000.00 of profit
Revenue of S$800,000.00, net profit before tax of S$120,000.00, and S$15,000.00 of depreciation added back. Nothing else moves the computation, so line 5 and line 20 are both S$135,000.00. The table is the pack's 24 lines as the engine issues them, items 1 to 23 with item 19 on two lines, and the last column is what each Copy button writes. The first 21 are Part B; the last 3 are the carry register. See what each item means, with the tax computed from it.
| Line | Label on the pack | Figure, S$ | Clipboard |
|---|---|---|---|
| 1 | Net profit/loss before tax per financial statements | 120,000.00 | 120000.00 |
| 2 | Less: separate source income | 0.00 | 0.00 |
| 3 | Less: non-taxable income | 0.00 | 0.00 |
| 4 | Add: non-tax-deductible expenses | 15,000.00 | 15000.00 |
| 5 | Adjusted profit/loss before other deductions | 135,000.00 | 135000.00 |
| 6 | Less: S14N renovation & refurbishment | 0.00 | 0.00 |
| 7 | Less: EIS enhanced deductions | 0.00 | 0.00 |
| 8 | Less: further deductions | 0.00 | 0.00 |
| 9 | Adjusted profit/loss before capital allowances | 135,000.00 | 135000.00 |
| 10 | Add: balancing charge | 0.00 | 0.00 |
| 11 | Less: unutilised capital allowances b/f | 0.00 | 0.00 |
| 12 | Less: current year capital allowances | 0.00 | 0.00 |
| 13 | Less: unutilised losses b/f | 0.00 | 0.00 |
| 14c | Add: net rental income | 0.00 | 0.00 |
| 15 | Add: interest income | 0.00 | 0.00 |
| 16 | Add: other taxable income | 0.00 | 0.00 |
| 17 | Total income before donations | 135,000.00 | 135000.00 |
| 18 | Less: unutilised donations b/f | 0.00 | 0.00 |
| 19a | Less: IPC donations | 0.00 | 0.00 |
| 19b | Less: PTIS/OHAS donations | 0.00 | 0.00 |
| 20 | Chargeable income before exempt amount | 135,000.00 | 135000.00 |
| 21 | Unutilised capital allowances c/f | 0.00 | 0.00 |
| 22 | Unutilised losses c/f | 0.00 | 0.00 |
| 23 | Unutilised donations c/f | 0.00 | 0.00 |
Then the 5 lines you do not type. The portal applies the partial tax exemption, the 17% rate and the YA 2026 rebate itself; the pack shows them so that the portal's figure can be checked against the engine's.
| Label on the pack | Figure to expect, S$ | Clipboard |
|---|---|---|
| Less: exempt amount | 70,000.00 | 70000.00 |
| Chargeable income after exempt amount | 65,000.00 | 65000.00 |
| Tax at 17% | 11,050.00 | 11050.00 |
| Less: corporate income tax rebate | 5,525.00 | 5525.00 |
| Net tax payable | 5,525.00 | 5525.00 |
The net tax line on the pack carries the pack's own verdict chip and the sentence: the portal computes this box itself, check it shows S$5,525.00 before you press submit. One case where the portal is right and the pack is not: a company with at least one local employee on CPF receives S$2,000 of the rebate as a cash grant instead of off the bill, so the portal will show a bill S$2,000 higher than this line. The app does not ask that question, so it takes the whole rebate off. See the grant, the cap and which company gets which.
Where the pack and the portal use different words
The pack numbers its lines in IRAS's Basic Tax Calculator order, which is also the order of the Part B items in IRAS's explanatory notes for lines 1 to 20. Two places need care.
- Rental income. The portal's item 14 is three boxes: gross rental income, the deductible expenses against it, and the net. The pack carries the net at line 14c. A company with rental income takes the gross and the expenses from its books.
- Lines 21 to 23. The pack's lines 21 to 23 are its carry register: the unutilised capital allowances, losses and donations carried forward, numbered in the Basic Tax Calculator's order. IRAS's Part B is items 1 to 20, and its explanatory notes pick up again at item 24, in Part C. The repo records no Form C-S box for these three figures, so type nothing from them, and do not assume the portal's items 21 to 23 are the pack's.
Line 19a on the pack is the deduction, not the gift: approved IPC donations count 2.5 times, a 250% deduction for donations made from 1 January 2016 to 31 December 2029. You record what you gave, and the pack applies the multiplier and shows the arithmetic. Type the pack's figure.
The pack, a copy button on every line
Post the year's documents, answer the questions the pack asks about the books, and the Tax screen issues the Form C-S: the 21 Part B lines in IRAS's own numbering, each with a Copy button and its arithmetic, the 5 portal-computed lines with the figure to expect, the 3-line carry register for next year, and a bar that remembers where you stopped. Simpler Tax files nothing and holds no Corppass credentials.
Download for WindowsQuestions people ask
Does Simpler Tax file Form C-S for me?
No. It prepares the figures and shows the working; you type them into myTax Portal and sign. It holds no Corppass credentials and sends nothing to IRAS. The pack says so on its own foot: only you can file it.
What exactly does the Copy button put on the clipboard?
The figure for that line as a bare number with two decimals: no S$, no commas. For the worked company line 5 copies 135000.00, and line 20 copies 135000.00. A line at 0.00 copies 0.00.
Which boxes does the portal fill in itself?
The exempt amount, the chargeable income after it, the tax at 17%, the YA 2026 rebate and the net tax payable. You do not type those. The pack lists them under "What the portal computes for you" so you can check the portal's figure against the engine's before you submit.
Do I type the pack's lines 21 to 23 anywhere?
No. They are the pack's carry register: the unutilised capital allowances, losses and donations that go into next year's opening when you close the year. IRAS's Form C-S Part B is items 1 to 20, and the repo records no portal box for these three. The portal's own items 21 to 23 are a different thing.
I was logged out halfway. Where was I?
The portal keeps a saved draft for 21 days or until 30 Nov 2026, whichever is later, so save before you stop. The pack keeps its own place: each line you copied stays ticked on your machine, and the bar at the top says "resume at line N" when you come back.
I am set up as a Preparer in Corppass. Can I submit?
No. A Preparer completes the return and passes it to an Approver; only an Approver submits to IRAS. The company needs at least one Approver, and the Approver is not alerted automatically when a Preparer hands a return over.
I submitted, then found a mistake. What now?
Use the portal's "Revise/Object to Assessment" digital service. For a Form C-S revision IRAS asks for the financial statements, the tax computation and the supporting schedules to be attached. Fix the books in Simpler Tax first, so the revised computation is the one the pack shows.
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.
- IRAS, Overview of Form C-S / Form C-S (Lite) / Form C
https://www.iras.gov.sg/taxes/corporate-income-tax/form-c-s-form-c-s-(lite)-form-c-filing/overview-of-form-c-s-form-c-s-(lite)-form-c - IRAS, FAQs on filing Form C-S (Corppass roles, the draft, the session timeout)
https://www.iras.gov.sg/media/docs/default-source/uploadedfiles/pdf/faqs---file-form-c-s.pdf - IRAS, FAQs on filing Form C (the Revise/Object to Assessment service and what a Form C-S revision attaches)
https://www.iras.gov.sg/docs/default-source/uploadedfiles/pdf/faqs---file-form-c.pdf - IRAS, Explanatory notes to the YA 2026 Form C-S (Parts A, B and C; Part B is items 1 to 20)
https://www.iras.gov.sg/docs/default-source/uploadedfiles/pdf/explanatory-notes-to-ya-2026-form-c-s.pdf - Partial tax exemption tiers, the exempt amount the portal computes rulebook cit.pte
- myTax Portal
https://mytax.iras.gov.sg - Form C-S eligibility, the four Part A conditions rulebook forms.cs.eligibility
- Filing deadline and e-filing rulebook forms.filing-deadline
- Corporate income tax rate rulebook cit.rate.headline
- YA 2026 corporate income tax rebate rulebook cit.rebate.ya2026.enhanced
- The 250% deduction for IPC donations and its window: research/tax-adjustments.md (IRAS, tax treatment of business expenses; MOF Budget 2026 Annex H-1), the multiplier the engine applies at line 19a, checked against it at build
- The pack's labels, chips, plates and copy buttons: app/src/main.mjs, the Tax pane (csSectionHtml, taxLineHtml, the copy column), and the close route in app/server.mjs; every string this page attributes to them is re-read from the file at build
- The portal facts: research/forms-cs.md, Corppass and portal process, verified against the IRAS FAQs 2026-07-24; every portal fact on this page is re-read from the note at build