Forex loss in tax return — how to file

A forex loss hurts, but properly filed it becomes a tax asset you can use for five more years under Polish law. The PIT-38 return turns it into a real deduction against future capital-gains income, thanks to article 9 paragraph 3 of the Personal Income Tax Act. The rules that govern it catch out traders who only think about tax after the fact: a five-year window, and a choice between deducting at most fifty percent of the loss each year or writing off up to 5 million PLN in one go. Here is how the mechanism actually works, with a worked example using a Polish broker and Polish zloty.

Is a forex loss tax-deductible in Poland

Yes. Polish tax law treats profit and loss from CFD trading on currency pairs as income from capital sources under article 30b of the Personal Income Tax Act — the same bucket that holds shares, ETFs and futures. You report all of it on a single annual return called PIT-38, with a flat 19 percent rate on net gains (the so-called Belka tax). One caveat: cryptocurrency goes on the same form but sits in its own separate part with its own rules, so a crypto loss does not offset a currency-market gain, and the reverse does not work either. If the capital-source bucket ends the year in the red, you can carry the loss into the future.

Three rules to memorize before your first filing:

• Five consecutive tax years to use the loss, counted from the year after it was incurred. A loss from 2024 expires after the 2029 filing season.
• Two deduction routes to choose from. The default one: at most 50 percent of the loss amount in any single one of those years, with the remainder carried forward. The alternative, available for losses incurred from 2019 onwards: a one-off reduction of income in one of the five years by up to 5 million PLN, with anything left over falling back to the fifty-percent rule in the remaining years.
• Within the same income source only. A forex loss can only reduce later capital-source gains. It will not offset salary, business income, or rental income from a separate source.

Contrary to a common piece of advice on Polish trading forums, simply reporting the loss costs nothing — the tax office will not refund tax against a loss. The paper trail matters because it is the only thing that gives you the right to deduct later. Skip the PIT-38 in a loss year and you have nothing to carry forward, regardless of how profitable the next year turns out.

How the fifty-percent cap works in practice

Illustrative example, not tax advice. Suppose a trader filing through a Polish broker closed 2024 with a 20,000 PLN net loss on EUR/USD and GBP/JPY pairs. In 2025 the account recovered and produced an 8,000 PLN gain, already net of commissions and platform fees. Without carryforward the tax on that gain would be 19 percent, namely 1,520 PLN. With the loss applied, the math looks different.

There is a subtlety worth pinning down. The fifty-percent ceiling refers to the original loss amount, not the balance you still have. That is why in 2027 the deduction could have been as high as 10,000 PLN even though only 6,000 PLN of the loss remained.

In this example the choice between the two routes changes nothing, because every annual gain is smaller than half the loss, so the deduction is limited by current-year income anyway. The one-off route only starts to matter when a single year brings a gain larger than half the loss: with a 100,000 PLN loss and 100,000 PLN of capital-source income in one of the five years, the whole thing can be written off at once instead of being spread across two years at 50,000 PLN each. With annual gains in the low tens of thousands, a large loss can still expire before it is fully used — the five-year window cannot be extended.

Filling in PIT-38 with a loss step by step

The mechanics, whether you use the Twoj e-PIT pre-filled portal or work through the paper form yourself:

1. Gather broker documents. Polish brokers and brokerage houses (XTB, DM BOS, the mBank brokerage arm) prepare a PIT-8C and deliver it to the taxpayer by the end of February, listing total revenue, total cost, and the year-end result. Foreign brokers operating without a Polish registration (IC Markets, Pepperstone, Interactive Brokers) do not issue PIT-8C, so you build the calculation yourself from the annual statement.
2. Fill in parts C and D of the PIT-38 — capital-source revenue and costs. A result from a foreign account is translated into zloty at the average NBP rate from the last business day preceding the day the revenue arose or the cost was incurred — not at the rate on the transaction day, and not at a single rate for the whole year.
3. Part E is where the loss lives. If costs exceed revenue, the negative balance goes here. This entry creates the right to deduct in the next five years.
4. On the following year's return, if you have a gain, return to part E and enter the deduction. Remember the cap of fifty percent of the original loss amount (or the one-off route of up to 5 million PLN, if that is the one you use), and that the deduction cannot exceed the current year's capital-source income.
5. File by 30 April — the simplest route is Twoj e-PIT, which pre-fills the form with PIT-8C data. Not filing a return in a loss year forfeits the carry-forward right.
6. Keep documents for five years from the end of the year in which the payment deadline fell. PIT-8C, the broker's annual statement, a trade ledger and account statements are the minimum if the tax office requests an audit.

One observation from watching the retail-trading market in Poland: small losses of one or two thousand zloty per year usually are not worth the bookkeeping if you do not plan to trade consistently. Larger ones — from around ten thousand upwards — should be reported without exception, because skipping them means giving up the right to offset future gains. The PIT-38 overview covers the rest of the return, and deductible costs explains what counts as a cost reducing your tax base. For wider context on record-keeping and reporting duties across jurisdictions, the ForexMechanics taxes and records section is a useful supplement.

What if you forgot to report a loss in a prior year

This is more common than you might think: a trader closes the year in the red, decides that no tax owed equals no return required, and finds out about the gap only when the next year ends in profit. The fix is a corrective filing — a PIT-38 marked as a correction — for the loss year. You can submit it until the statute of limitations runs out, namely five years from the end of the year in which the payment deadline fell. Alongside the correction it is worth filing a so-called czynny zal, a voluntary disclosure under the Polish fiscal penal code that mitigates any potential sanction.

The correction itself does not trigger a penalty if your earlier omission did not understate any tax due. In a loss year you simply file the missing return and recover the right to carry forward. That separates Poland from jurisdictions where missing the deadline closes the door permanently.

„By the amount of a loss from a source of income incurred in a tax year, the taxpayer may: 1) reduce the income obtained from that source in the next five consecutive tax years, provided that the amount of the reduction in any of those years does not exceed 50% of that loss, or 2) reduce, on a one-off basis, the income obtained from that source in one of the next five consecutive tax years by an amount not exceeding PLN 5,000,000 (…)." — Personal Income Tax Act, article 9 paragraph 3, Dz.U. 1991 Nr 80 poz. 350, 1991 (translation of the Polish original).

Common mistakes and interpretive traps

These are the things that most often spoil loss filings for Polish retail forex traders:

• Mixing sources. A currency-market loss will not reduce tax on salary, on rental income or on business income — it works only inside capital sources. It will, however, offset a gain on shares or futures without any trouble, because that is one and the same source under article 30b. If you want to trade inside a company, a different regime applies, as the forex as a company article explains.
• Counting the cap against the balance, not the original amount. The fifty-percent ceiling refers to the same number every year — the loss as originally reported. Two partial deductions do not shrink the ceiling.
• Not knowing the one-off route exists. For losses incurred from 2019 onwards the fifty-percent rule is not the only option. With a loss of several tens of thousands of zloty and one genuinely good year, the one-off deduction settles the whole thing in a single return.
• Omitting costs from a foreign broker. Commissions, negative swap points and fees charged to the account all feed into the result; leave them out and the reported loss will be smaller than the real one. The spread is not a separate item here, because it is already contained in the opening and closing prices of the position.
• Assuming no PIT-8C means no obligation. If your broker does not issue the form, you still have to report the result. The platform's annual statement plus a translation into zloty at the correct average NBP rates is enough evidence.

What to do tomorrow

1. Log into your broker's portal and download annual transaction statements for the last five years — this is the foundation for checking whether any closed year was a loss you never declared. Without these statements, no honest calculation of what is still available to deduct is possible.
2. Open every PIT-38 you filed in the last five years (they are stored in the Twoj e-PIT service) and look at part E — write down on paper how much loss is still available to use from each origin year. The fifty-percent ceiling is calculated against the original amount, not the running balance.
3. Decide which of the upcoming years should host the largest deduction — savings are biggest in years with high capital-source income, so it can pay to wait one year and apply the loss against a larger gain rather than spending the ceiling on a small result.
4. If you missed reporting a loss in a previous year, prepare a corrective PIT-38 together with the so-called czynny zal — both are formalities, but they require written form and concrete reasoning, so do not leave them for the deadline day.
5. Book a session with a Polish tax adviser (typically 200 to 400 PLN) if your loss exceeds about fifteen thousand zloty, or if you traded with a broker outside the European Union — both cases bring details that affect the deductible amount more than the basic filing duty.