Corporate Action Calculator: Splits, Bonus & Rights
What a split, bonus, rights issue or demerger does to your shares and cost.
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For education only, not investment advice: no tool here tells you what to buy, sell or hold. Results use only the figures you enter, the files you load (read in your browser, never uploaded) and the published rules each page names. Check them against your broker's or exchange's own figures, and consider a licensed or registered adviser for advice on your situation.
About the Corporate Action Calculator: Splits, Bonus & Rights
A company’s corporate actions change how many shares you hold, and so what each one cost you, without your doing anything. This calculator works out the result of each kind: a split (5 new shares for 1), a consolidation or reverse split (1 for 10), a bonus issue or stock dividend (1 bonus share for every 2 held), a rights issue — your entitlement, the theoretical ex-rights price (TERP), what a right is worth and what taking them up costs — and a demerger or spin-off, with your cost split between the two companies by the share the company announces.
It shows the new number of shares, the cost per share (the total cost stays the same, except for money you pay for rights shares), fractions of a share sold for cash, and the factor that makes prices from before the action comparable with prices after it. Where the tax rules are clear — India, the UK and the US — it says how they treat the action and links the official text; the capital gains tools of each country do the rest. Nothing you type leaves your browser.
How to use it
- Choose the action: a split, a consolidation, a bonus issue, a rights issue or a demerger.
- Enter the shares you hold and what they cost you, as a total or a cost per share.
- Enter the ratio as the company announced it (for example 1 new share for every 4 held), and for a rights issue the subscription price, the price before the issue and the rights shares you take up.
- For a demerger, enter the share of the cost that stays with your shares (the company’s apportionment for your country’s tax).
- Read the new number of shares and the cost per share, and the table before and after; then copy the summary or download the table as CSV — with a pass, or after unlocking this result.
Examples
100 DEMO shares that cost 500 each (50,000 in all)
500 shares at 100 each; the total cost stays 50,000
Bonus: 100 shares · consolidation: 1,000 shares at 2
Bonus: 200 shares, the average cost halves · consolidation: 100 shares at 20
100 ABC Ltd shares that cost 500 each; price before the issue 100; all 25 rights shares taken up
TERP 96 · a right is worth 16 a new share (4 a share held) · 25 new shares cost 2,000 · 125 shares, 52,000 in all: 416 a share
100 shares that cost 10,000; 80% of the cost stays with them
Your shares: 8,000 (80 a share) · 50 new-company shares: 2,000 (40 a share)
Common uses
- Update your cost per share after a split or a bonus issue.
- Decide with the numbers whether to take up, sell or let lapse the rights of a rights issue.
- Split your cost between two companies after a demerger.
- Adjust old prices and charts for a split, bonus or rights issue.
The formulas
- Split of b new shares for a: shares × b ÷ a; cost per share × a ÷ b.
- Consolidation of 1 new share for n: shares ÷ n; cost per share × n.
- Bonus issue of b for every a held: shares × (a + b) ÷ a; the total cost is spread over all of them.
- Rights issue of m new shares for every n held at the price S, the price before the issue being P: TERP = (n × P + m × S) ÷ (n + m). A right is worth TERP − S for each new share, or (TERP − S) × m ÷ n for each share held; taking up X new shares costs X × S, which is added to the holding’s cost.
- Demerger of k new-company shares for every a held: new-company shares = shares × k ÷ a; the cost that stays = total cost × the announced share; the rest goes to the new-company shares.
- Price adjustment: prices from before the action × a ÷ b (split), × a ÷ (a + b) (bonus), × TERP ÷ P (rights), × the share that stays (demerger) compare with prices after it.
- Fractions of a share are usually sold and paid as cash in lieu; the fraction takes its share of the cost with it.
Tax notes by country
- India: bonus shares cost nil for capital gains, your original shares keep the price you paid, rights shares you subscribe for cost the amount paid, and rights you renounce cost nil (Income-tax Act, 2025, section 90(6)). The average cost this calculator shows is the economic one, not the tax cost: see the capital gains tax calculator and the FIFO capital gains calculator.
- United Kingdom: a bonus or rights issue is a reorganisation, not a disposal; the new shares count as bought when your existing ones were, in the same holding (HMRC Capital Gains Manual, CG51700). The UK capital gains tax calculator works out the gain.
- United States: for a split or a nontaxable stock dividend of the same stock, the old basis is divided by the number of old and new shares; nontaxable rights worth 15% or more of the old stock take a share of its basis, and new shares from exercised rights cost their price plus the basis of the rights (IRS Publication 550). See the US capital gains tax calculator.
- Elsewhere, and for demergers, follow the apportionment and the rules your tax authority publishes.
Reading the results
- New number of shares: whole shares, with any fraction sold for cash (or kept, where your broker holds fractions).
- Cost per share: the economic cost after the action. Your total cost changes only by money you pay for rights shares, and by the fraction sold.
- TERP is the price a share should have once the rights are issued, if nothing else changes; the market price can differ.
- Price adjustment: older prices and charts compare with today’s once multiplied by it.
What it leaves out
- Mergers and takeovers paid in shares and cash, and share buybacks: their terms are each their own.
- Your tax: the notes say how three countries treat these actions; the gain itself is for the country tools.
- Market prices after the action: the TERP and the adjustment are theoretical; the price you can sell at is the market’s.
Limitations
- The ratio and the apportionment are the company’s: type them as announced; when they differ by country, use your country’s.
- Cash in lieu of fractions is shown at the price you type; the company sets the real one.
- The tax notes cover what the official texts linked here say, for India, the UK and the US only.
- This is a calculation of what an action does to your holding, not advice on what to do with it.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
What do I get without a pass?
Without a pass, Corporate Action Calculator: Splits, Bonus & Rights shows the new number of shares in full, with the first rows of each table and the first step of the working; every other figure is hidden. Until you unlock it, the result can’t be downloaded or copied. A Pro, Premium or Ultimate pass, a one-time payment that never renews, unlocks the full result. The pricing page lists the passes and their prices.
What happens to my cost per share after a stock split?
Your total cost stays the same and is spread over more shares. In a 5-for-1 split, 100 shares that cost 500 each become 500 shares that cost 100 each: 50,000 in all, before and after.
How do I work out the theoretical ex-rights price (TERP)?
TERP = (n × the price before the issue + m × the subscription price) ÷ (n + m), for m new shares for every n held. For 1 new share for every 4 at 80, with the price at 100 before: (4 × 100 + 80) ÷ 5 = 96.
What is a right worth in a rights issue?
In theory, the TERP minus the subscription price for each new share it lets you buy: 96 − 80 = 16 in the example, or 4 for each share you hold when you get 1 right for every 4 shares. If the subscription price is at or above the market price, the rights are worth nothing.
Do bonus shares change my cost?
Your total cost does not change, so the average cost a share falls: a 1-for-1 bonus halves it. For tax, countries differ: in India bonus shares cost nil and your original shares keep their cost; in the UK they join your existing holding as if bought with it.
How is the cost split in a demerger?
By the share the company announces for your country’s tax, which can differ between countries. Enter the share that stays with your existing shares; the rest is the cost of your new-company shares.
What happens to fractions of a share?
Usually the company sells them and pays you cash in lieu, and that sale carries the fraction’s part of your cost. Some brokers keep fractional shares instead: choose to keep them and the calculator does not round.