Why does it ask for two exchange rates on every sale?

Because the acquisition value and the disposal value are each converted at the rate on their own settlement date. They are usually months or years apart, so they are usually different rates, and that difference is part of the taxable gain rather than a rounding detail. Applying one average rate to both sides removes the currency effect from the calculation entirely and produces a number that does not match the filing. Two fields per sale is more typing, but a single-rate calculator gives a confidently wrong answer, which is worse.

Where do I find the right exchange rate?

Your brokerage's transaction history is the easiest source — it records the rate applied to each settled trade, which is the figure you want. The same rate is published daily as the base rate, so a historical rate table for the settlement date works too. Two things to avoid: the trade date rather than the settlement date, and an annual average. Both are close enough to look plausible and far enough to change the tax.

Do I really have to enter my losing trades?

You should, because they reduce what you are taxed on. Gains and losses in the same tax year are netted before the deduction is applied, so a loss on one holding directly lowers the tax owed on another. Leaving losses out therefore overstates the bill — sometimes by a lot, if the year contained a large one. The only thing a loss cannot do is travel: an unused loss does not carry into the next tax year, so it is worth entering in the year it happened.

Is the deduction per stock or per year?

Per year, across all overseas share sales combined. This is the single most common error in do-it-yourself estimates: calculating each holding separately and giving each one its own deduction, which understates the tax as soon as there is more than one sale. It also does not carry over — an allowance you did not use is simply gone when the year ends, which is why some people time a sale to use it up.

The share price barely moved but there's tax to pay. How?

The gain is measured in won, not in the listing currency. If the won weakened between your buy settlement and your sell settlement, the same number of dollars converts into more won, and that increase is a taxable gain even though the position went nowhere in its own currency. The currency panel in this calculator exists for exactly this situation — it shows how much of the gain came from the share price and how much came from the rate, so the tax bill stops looking arbitrary.

Does this cover Korean domestic shares?

No, and mixing them in would give a wrong answer. Domestic listed shares are generally not subject to capital gains tax for ordinary investors — that treatment applies to large shareholders, under thresholds and rules of their own. What ordinary domestic trades do carry is a transaction tax charged on each sale, which is a per-trade cost rather than an annual gains calculation. Use a stock return calculator for that side.

When and how is this actually filed?

Overseas share gains are reported in the capital gains tax return filed in May of the following year, covering sales settled during the previous year. Some brokerages offer an assisted filing service that collects the figures for accounts held with them, which is convenient but only covers that one brokerage — if you traded through several, the netting across all of them is still yours to do. The rate in this calculator already includes local income tax, so the figure shown is the combined amount rather than the headline rate alone.

Is this good enough to file with?

Treat it as an estimate for planning, not as a return. It reproduces the published method, but a filing depends on details this tool does not see: the exact settlement dates and rates your brokerage applied, expenses you may have forgotten, sales through other brokerages, and any circumstances specific to you. Its real use is answering questions before the year ends — whether a further sale would push you past the deduction, or how much of the bill is currency rather than performance. Confirm the final number against your brokerage's statements or with a tax professional.

Does this tool upload my data?

No. Everything runs right in your browser, so your data never leaves your device — it even works offline once the page has loaded. Your entries are kept in your browser's own storage so the year you were working on is still there when you come back, and clearing your browser data removes them.

🌏 Overseas Stock Capital Gains Tax Calculator

Two things make this calculation different from a domestic one, and both are easy to get wrong. The deduction is annual, not per stock, so a tax bill cannot be worked out one holding at a time — and a loss on one position genuinely reduces the tax on another. The gain is also measured in won, which means the exchange rate is part of the taxable amount: a position that moved sideways in dollars can still produce a taxable gain if the won weakened between the two settlement dates. This calculator takes every sale for the year, applies the deduction once at the end, and shows the currency's contribution as its own line.

A capital gains tax calculator for Korean residents selling overseas-listed shares. It nets every sale in a tax year together, applies the annual deduction once rather than per stock, converts the buy and the sell side at their own exchange rates, and separates how much of the resulting gain came from the share price and how much came from the currency.

One tax year at a time

The deduction is granted once per year across every overseas sale, not once per stock. So enter every sale you settled in the same year — gains and losses both, because losses reduce the total you are taxed on.

Annual deduction (기본공제, KRW)

Tax rate (세율, %)

Net gain for the year (연간 양도차익)

—

Taxable amount (과세표준)

—

Tax due (산출세액)

—

How much of it was the stock, and how much was the exchange rate

Your gain is measured in won, so a currency move changes your tax bill even when the share price did not move at all. This splits the two apart.

Sale by sale

Read this before you rely on it

This is an estimate, not a filing. The National Tax Service converts each side at the exchange rate on its own settlement date, which is why this calculator asks for two rates per sale rather than one — a single average rate gives a different answer, and it is the wrong one. The deduction amount and the rate are editable because tax law changes; confirm both against the current rules before you file.

Overseas share gains are declared in the capital gains tax return the following May, and the rate here already includes local income tax.

Domestic Korean shares are not covered here. They are only taxed this way for large shareholders, under a separate set of thresholds.

Private by design. This tool runs entirely in your browser — nothing you enter is uploaded or stored, and it works offline.

About

The sequence matters. Each sale is converted to won on its own terms first: the acquisition value is the buy price times the quantity times the exchange rate on the buy settlement date, and the disposal value uses the sell settlement date's rate. Deductible expenses come off, and what remains is that sale's gain. Only then are the sales added together, the annual deduction subtracted once, and the rate applied to whatever is left. Running the deduction per stock instead — the most common mistake — understates the tax whenever there is more than one sale.

Using two exchange rates rather than one average is not a refinement; it is the method. Each side is converted at the rate on its own settlement date, so a single rate applied to both produces a different number, and the difference grows with the size of the currency move. This calculator therefore asks for two rates per sale, which is why it has more fields than a simpler tool would.

The currency split exists because the tax rarely feels intuitive without it. The gain from the share price is the price move times the quantity at the buy-side rate; the gain from the currency is the sell-side value times the change in rate. Those two add to exactly the pre-expense gain, so nothing is lost in the decomposition. When the currency line is larger than the price line, the panel says so — a warning that the tax bill is being driven by something other than stock picking.

Losses count. Enter them with a sell price below the buy price and they reduce the annual total, which is the whole point of netting. What they do not do is carry forward: an unused loss, like an unused deduction, does not travel to the next tax year.

Deduction and rate are both editable because both are set by tax law and law changes. The rate field expects the headline rate with local income tax already included, since that is how the bill actually arrives.

How to use

Work one tax year at a time. Set the annual deduction and the rate at the top, checking both against the current rules rather than trusting the defaults — they are written into tax law and revised from time to time.
Enter your first sale: how many shares, the buy and sell price in the listing currency, and the exchange rate that applied on each settlement date. Two rate fields is not a mistake — each side is converted on its own date, and using one average rate for both gives the wrong answer.
Add the commission and any local charges on that sale, converted to won. They are deductible expenses, so they lower the gain. Leaving the field at zero is safe — the tax simply comes out slightly high.
Add every other sale you settled in the same year, losses included. This is the step people skip, and skipping it costs money: a loss on one holding reduces the taxable total from the others, and the deduction is shared across all of them rather than granted to each.
Read the three cards: the netted gain for the year, the taxable amount after the deduction, and the tax itself. If the gain sits inside the deduction the tax is zero, and the panel tells you how much more you could still realise this year before any tax starts.
Check the currency panel. It splits the gain into the part the share price produced and the part the exchange rate produced. If the currency line is the bigger one, your tax is being driven mostly by the won, which is worth knowing before you decide when to sell the rest.

FAQ

Why does it ask for two exchange rates on every sale?: Because the acquisition value and the disposal value are each converted at the rate on their own settlement date. They are usually months or years apart, so they are usually different rates, and that difference is part of the taxable gain rather than a rounding detail. Applying one average rate to both sides removes the currency effect from the calculation entirely and produces a number that does not match the filing. Two fields per sale is more typing, but a single-rate calculator gives a confidently wrong answer, which is worse.
Where do I find the right exchange rate?: Your brokerage's transaction history is the easiest source — it records the rate applied to each settled trade, which is the figure you want. The same rate is published daily as the base rate, so a historical rate table for the settlement date works too. Two things to avoid: the trade date rather than the settlement date, and an annual average. Both are close enough to look plausible and far enough to change the tax.
Do I really have to enter my losing trades?: You should, because they reduce what you are taxed on. Gains and losses in the same tax year are netted before the deduction is applied, so a loss on one holding directly lowers the tax owed on another. Leaving losses out therefore overstates the bill — sometimes by a lot, if the year contained a large one. The only thing a loss cannot do is travel: an unused loss does not carry into the next tax year, so it is worth entering in the year it happened.
Is the deduction per stock or per year?: Per year, across all overseas share sales combined. This is the single most common error in do-it-yourself estimates: calculating each holding separately and giving each one its own deduction, which understates the tax as soon as there is more than one sale. It also does not carry over — an allowance you did not use is simply gone when the year ends, which is why some people time a sale to use it up.
The share price barely moved but there's tax to pay. How?: The gain is measured in won, not in the listing currency. If the won weakened between your buy settlement and your sell settlement, the same number of dollars converts into more won, and that increase is a taxable gain even though the position went nowhere in its own currency. The currency panel in this calculator exists for exactly this situation — it shows how much of the gain came from the share price and how much came from the rate, so the tax bill stops looking arbitrary.
Does this cover Korean domestic shares?: No, and mixing them in would give a wrong answer. Domestic listed shares are generally not subject to capital gains tax for ordinary investors — that treatment applies to large shareholders, under thresholds and rules of their own. What ordinary domestic trades do carry is a transaction tax charged on each sale, which is a per-trade cost rather than an annual gains calculation. Use a stock return calculator for that side.
When and how is this actually filed?: Overseas share gains are reported in the capital gains tax return filed in May of the following year, covering sales settled during the previous year. Some brokerages offer an assisted filing service that collects the figures for accounts held with them, which is convenient but only covers that one brokerage — if you traded through several, the netting across all of them is still yours to do. The rate in this calculator already includes local income tax, so the figure shown is the combined amount rather than the headline rate alone.
Is this good enough to file with?: Treat it as an estimate for planning, not as a return. It reproduces the published method, but a filing depends on details this tool does not see: the exact settlement dates and rates your brokerage applied, expenses you may have forgotten, sales through other brokerages, and any circumstances specific to you. Its real use is answering questions before the year ends — whether a further sale would push you past the deduction, or how much of the bill is currency rather than performance. Confirm the final number against your brokerage's statements or with a tax professional.
Does this tool upload my data?: No. Everything runs right in your browser, so your data never leaves your device — it even works offline once the page has loaded. Your entries are kept in your browser's own storage so the year you were working on is still there when you come back, and clearing your browser data removes them.