What yen intervention is
Foreign exchange intervention is a trade by the monetary authorities to stabilise exchange rates. In Japan the Minister of Finance has the legal power to decide it, under the Foreign Exchange and Foreign Trade Act.
The Bank of Japan does the trading, on the Minister's instructions and as the government's agent. The timing and the amount are the Ministry's call.
The money comes from the Foreign Exchange Fund Special Account, a government account. To buy yen, it sells dollars it holds. To sell yen, it raises yen by issuing financing bills.
How the market learns about it
The Ministry of Finance publishes the total amount of intervention for each monthly period at the end of the month. A quarterly report follows a few weeks after the quarter ends, with each day of intervention, the amount and which currency was sold and which was bought.
On the day itself, the market sees a sudden, large move in the yen. Officials may confirm the action, decline to comment, or leave it to the monthly figure, and until then traders work from the price and from the wording.
Why warnings about yen intervention matter
Officials often speak before they act. The Minister of Finance and the Vice Minister of Finance for International Affairs comment on the yen when it moves fast, and sharper words are read as a sign that action is closer.
Those words alone can slow a move, because traders do not want to be caught on the wrong side of a large official trade. The market calls this verbal intervention.
Warnings are not a timetable. The Ministry can wait a long time after strong words, so the risk of a sudden reversal stays with the yen for as long as the move it worries about goes on.
How to read intervention risk
Intervention can go either way: buying yen to stop it falling, or selling yen to stop it rising. Either way the first thing to watch is the speed of the move, not only its size.
A round of intervention can turn the yen sharply, but the effect can fade if the gap between Japanese and foreign interest rates keeps pulling the other way. What the Bank of Japan and the Federal Reserve do next matters for how long it lasts.
An entry such as intervention watch in a calendar marks a period of higher risk, when the yen has moved far and fast and officials have stepped up their language. It is not a scheduled event.
What the Japanese yen did on the last release days
Our calendar keeps the exact time of each release since 16 September 2026. The first Yen intervention after that date will show here with the Japanese yen's move around it.
For scale: on an ordinary day the Japanese yen moves 0.24% against the basket from one London opening to the next, either way, on average over the 250 trading days since 14 Oct 2025.
The forecast, the figure itself and what it changed in our view of the currency are in the app, next to the research.