Which cost is used when I bought the same share several times?

First in, first out. Portugal matches a disposal against the oldest acquisitions still open, and Miw does the same — which is why the report is built from your whole statement history rather than from one year in isolation.

Do I have to declare a year in which I lost money?

Losses are declared exactly as gains are. The year is assessed on the net balance, so a loss left out is a deduction thrown away. Miw includes every closed position, whether it ended up or down.

What exchange rate is used for a share bought in dollars?

The rate your broker booked on that operation, taken from the statement itself rather than looked up afterwards. That keeps the euro figures consistent with the account they came from.

IRS · Anexo G

Declaring share capital gains: Anexo G or Anexo J

A Portuguese resident reports what they made — or lost — selling securities in Anexo G, or in Anexo J when the broker is abroad. The figures either one wants are not the ones a broker shows you: it asks disposal by disposal, matched to the particular lots you bought, in euros, with the fees kept separate. That is arithmetic over your entire statement, and it is what Miw does.

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Which annex: it depends on the broker

Category G income — mais-valias. Where it goes depends on who holds the account, not on where the company is from. A broker established in Portugal reports your sales to the tax authority, so they go in Anexo G, Quadro 9. One that does not — DEGIRO, Trading 212, Interactive Brokers — makes them income obtained abroad: Anexo J, Quadro 9.2A, code G01, with the broker’s country as the counterparty. Either way you declare each disposal, and losses belong in the same place, because the year is assessed on the net balance.

The rate, and when you stop being able to choose

The net balance is taxed at an autonomous rate of 28%. You may instead opt to aggregate it with your other income (englobamento), which is only worth doing when your marginal rate is lower. Aggregation stops being optional in one specific case: when the securities were held for less than 365 days and your taxable income, including this balance, reaches the top bracket — both conditions together, not either one. That is precisely why Miw flags positions approaching one year.

What Miw gives you

Import your statement and the table is built from the ledger, in the annex your broker belongs to — one row per closed lot, FIFO-matched, ready to transcribe or export to Excel or PDF:

Country of the issuer, taken from the ISIN prefix.
The security and its ISIN, with the quantity disposed of.
Acquisition year-month and value, and realization year-month and value, in euros.
Expenses and charges — the buying and selling fees for that lot.

Questions

Which cost is used when I bought the same share several times?: First in, first out. Portugal matches a disposal against the oldest acquisitions still open, and Miw does the same — which is why the report is built from your whole statement history rather than from one year in isolation.
Do I have to declare a year in which I lost money?: Losses are declared exactly as gains are. The year is assessed on the net balance, so a loss left out is a deduction thrown away. Miw includes every closed position, whether it ended up or down.
What exchange rate is used for a share bought in dollars?: The rate your broker booked on that operation, taken from the statement itself rather than looked up afterwards. That keeps the euro figures consistent with the account they came from.

Descriptive, not tax advice. Miw reads your statement and arranges the figures the way the annex asks for them; confirm the codes and your own circumstances with a tax professional.

Start from your broker

The figures come from the statement your broker already gives you — nothing is typed in by hand.

Import your statement