# Demerger cost base splits from ATO class rulings When an ASX company demerges, the ATO publishes a class ruling that says how to split your cost base between the shares you had and the ones you received. You get that split with each demerger, along with share splits and consolidations. [ Start for free ](https://app.quova.io/signup/) [ API reference ](https://quova.io/docs/income-and-corporate-actions/index.md#income.corporateActions) GET `/v1/corporate-actions` 1 credit per instrument ```shell curl "https://api.quova.io/v1/corporate-actions?symbols=ASX:BHP,ASX:ACE&from=2015-01-01&to=2023-12-31" \ -H "Authorization: Bearer $QUOVA_API_KEY" ``` Response 200 OK 2 credits ```json { "data": [ { "symbol": "ASX:BHP", "instrument": { "id": "ins_34VMvft6kZEXThtzFGcAL", "symbol": "ASX:BHP", "name": "BHP Group Ltd", "type": "equity", "mic": "XASX", "currency": "AUD", "country": "AU" }, "asOf": "2015-05-24T00:00:00Z", "actions": [ { "type": "demerger", "status": "completed", "effectiveDate": "2015-05-24", "announcedDate": "2014-08-19", "demerger": { "childName": "South32", "child": "ASX:S32", "ratio": 1, "au": { "costBaseApportionmentPct": 7.1 } } } ] }, { "symbol": "ASX:ACE", "instrument": { "id": "ins_34VN9N07Go23ZrlLllFc9", "symbol": "ASX:ACE", "name": "ACUSENSUS LIMITED.", "type": "equity", "mic": "XASX", "currency": "AUD", "country": "AU" }, "asOf": "2023-07-27T00:00:00Z", "actions": [ { "type": "split", "status": "completed", "effectiveDate": "2023-07-27", "announcedDate": "2023-06-23", "split": { "old": 1, "new": 5 } } ] } ], "errors": [], "meta": { "credits": 2, "requestId": "req_34VoxwVB3DzylkFGYbJQh" } } ``` ## How the split works A demerger doesn't add to your cost base. The ATO divides what you paid between the parent and the new company, often in proportion to their market values in the first days of trading. `costBaseApportionmentPct` is the part that moves to the demerged company. BHP's demerger of South32 in May 2015 shows how it works. [Class ruling CR 2015/40](https://www.ato.gov.au/law/view/pdf/pbr/cr2015-040.pdf) puts 7.1% of the cost base on South32 and leaves 92.9% with BHP, based on the volume weighted average prices of both over the five trading days after 18 May 2015\. If you'd paid $10,000 for your BHP shares, $710 of that became the cost base of your South32 shares and $9,290 stayed with BHP. ## Demergers covered Each percentage is the one the ATO's class ruling sets for that demerger. A few examples, with the ruling to check them against: | Demerger | Year | Ruling | To the new company | | ---------------------------------- | ---- | ---------- | ------------------ | | BHP to South32 | 2015 | CR 2015/40 | 7.1% | | Woolworths to Endeavour Group | 2021 | CR 2021/50 | 14.19% | | Tabcorp to The Lottery Corporation | 2022 | CR 2022/58 | 82.24% | For some older demergers, like Tabcorp's 2011 demerger of Echo Entertainment, the ATO published the split apart from the ruling, and the field is null for now. Demergers are covered for companies listed on the ASX. ## Splits and consolidations The same endpoint returns share splits and consolidations with the old and new share counts. ASX coverage is complete from December 2019\. Earlier ASX splits and those on other exchanges go back to 1980, and are most complete for US listings. ## Questions Either the ATO hasn't published its ruling yet, or it's an older demerger where the ATO published the split separately. We don't fill in a number the ATO hasn't set. It's the split the ATO's class ruling sets for the shareholders it describes. If your situation is unusual, like holding through a trust or not being an Australian resident, read the ruling itself. Yes, ratio is the new shares you get for each share held, as the ATO's ruling states it. It's null when the ruling doesn't give one. The endpoint has types for them, but we don't cover them yet, so they don't appear. Some returns of capital show up in the dividends endpoint with a type of return\_of\_capital. 1 credit per instrument. It's included in every plan, Free included, and in the trial. Anything that comes back as an error isn't billed. ## More tax data and tools - [**Exchange rates for tax** The rates the RBA, ATO, HMRC, IRS, ECB and Bank of Canada publish, apart from market FX.](https://quova.io/data/tax-exchange-rates/index.md) - [**ASX dividends and franking** Franked percentage, franking credit, company tax rate and DRP price for every ASX dividend.](https://quova.io/data/au/asx-dividends/index.md) - [**AMIT trust tax components** The tax components of each distribution from ASX listed ETFs and trusts, estimates and finals.](https://quova.io/data/au/amit-tax-components/index.md) - [**Tax exchange rate converter** Convert foreign income and sales into AUD, GBP or USD at the rate your tax office publishes.](https://quova.io/tools/tax-exchange-rates/index.md) - [**AMIT cost base calculator** Work out an ETF's cost base after years of AMIT adjustments, and the gain when you sell.](https://quova.io/tools/au/amit-cost-base/index.md) - [**Franking credit calculator** Gross up a franked dividend and see the tax you owe on it, or the refund, at your marginal rate.](https://quova.io/tools/au/franking-credits/index.md) ## Try every endpoint for 7 days The trial has 1,000 credits and full API access, and you don't need a card for it. After that you keep a free plan for personal projects, and paid plans start at $29 a month. [ Start for free ](https://app.quova.io/signup/) [ See pricing ](https://quova.io/pricing/index.md)