For small private companies — not too many transactions (around 50), simple or loss-making. Upload a CSV or type five figures, confirm how each line is classified, and get the computation in the standard Singapore format, including unutilised losses carried forward and which number goes in which Form C-S box. It is a first draft for professional review, not tax advice. If your situation needs an accountant, it says so instead of guessing.
| Runs | 100% in your browser — your file is never uploaded anywhere |
| Input | CSV template (roughly ≤50 rows) or typed P&L figures |
| Output | SG-format draft computation · loss c/f schedule · Form C-S box map |
| Cost | Free |
| Won't do | Foreign income, related-party loans, group relief, GST — it abstains and tells you why |
The computation engine is developed against a golden test suite: real professor-verified exam computations, a Deloitte-senior-tax-manager-reviewed client case, and synthetic edge cases. Every change must reproduce every verified number exactly before it ships. The current page runs a provisional engine while the verified build is finalised — the output footer tells you which one produced your draft.
Anything where a wrong draft could cost you real money: foreign income, director or related-party loans, group relief, investment holding, more than 50 transactions, revenue above S$200k. It stops, names the trigger, and tells you what an accountant needs to look at.
Nowhere. Parsing, classification, and computation run as JavaScript in this tab. There is no upload, no account, no server-side storage. Close the tab and it's gone.
This tool produces a draft computation and shows which figures correspond to which Form C-S fields on myTax. You (or your accountant) still review and file yourself — OpenTax SG never files anything.