Total Average vs Moving Average for Crypto in Japan

Japan gives individuals exactly two ways to compute the cost of crypto they dispose of, and requires a formal election to use the one that is not the default. Most people find out about the election after the deadline has passed, which is how they end up on a method they did not choose.

One correction first, because the opposite is widely repeated: the method is not irreversible. There is a published procedure to change it. It has conditions, and it is not retroactive, but it exists.

The two methods

FAQ section 2-4 explains that disposal cost is computed from the value of the crypto held at 31 December, using either the total average method or the moving average method.

Total average method. One average acquisition cost per crypto asset type for the whole year, computed from all acquisitions in the year. Every disposal in the year uses the same figure, including disposals that happened before the later purchases that changed the average.

Moving average method. The average is recomputed at each acquisition, and each disposal uses the average as it stood at that moment. It tracks the economics of the individual trade far more closely.

Over the entire life of a holding the two converge. Within any single year they can differ a lot, and in Japan a single year is what you are taxed on.

The election, and the default that catches people

FAQ section 2-5 sets out the procedure. The method is selected per type of crypto asset. Where you acquire crypto for the first time, or acquire a different type of crypto asset, you must file a notification of valuation method for crypto assets for income tax with the head of your competent tax office, by the filing deadline for the year of that acquisition, which is generally 15 March of the following year.

Then the line that decides most people's method for them: where no notification is filed, the valuation method is the total average method. The default is not a neutral outcome, it is a choice made by inaction, and because the election is per asset type, buying a new token creates a fresh obligation to elect for that token.

Changing method later

FAQ section 2-6 is the part usually left out. To change, you file an application for approval of change of valuation method for crypto assets for income tax with your competent tax office by 15 March of the year in which you want the change to apply, and obtain approval. Three points from its notes:

• If no notice of approval or rejection is given by 31 December of the year you file the application, approval is deemed to have been given on that day.
• The application may be rejected where a reasonable period has not passed since you adopted the current method. The section states that, absent a special reason, that period is three years.
• It may also be rejected where the method you want would make it difficult to compute income properly.

So the honest summary is: it is changeable, prospectively, subject to approval, and normally not more often than every three years. That is a meaningful constraint, which is presumably why the shorter and wrong version circulates.

Which to choose

There is no universally better method, and anyone who tells you otherwise is guessing about your trading pattern.

• Few trades, buy and hold. The two rarely diverge much. Total average is simpler and is what you get by default.
• Frequent trading in the same token, especially with large swings within a year. Moving average usually reflects the actual result of each trade far better. Total average can produce a taxable gain on a trade that lost money, because a large purchase later in the year lifted the annual average.
• Many different tokens. Remember the election is per type, so a moving average preference has to be filed for each one as you acquire it.

The decisive point is that this is not a calculation you can defer. The election deadline runs from the year of first acquisition of each asset, and the change deadline is 15 March of the year you want the change to bite. Both fall before you know what the year will look like.

Our crypto tax calculator computes disposal cost under either method, and the Japan crypto tax guide covers the rest of the return.

General information, not tax advice. Confirm the election and change procedures for your own case with the National Tax Agency or a qualified tax professional.

Practical Record-Keeping for Your Crypto Cost Method

Choosing between the total average method and the moving average method is only half the battle. The other half is keeping records that let you actually apply your chosen method correctly. Without solid records, you cannot compute the average acquisition cost accurately, and you cannot support your figures if the tax office asks questions. Start by organizing your transaction history from every exchange, wallet, and peer-to-peer trade. For each transaction, record the date, the type and amount of crypto acquired or disposed of, the value in yen at the time of the transaction, and any fees paid. If you use multiple platforms, consolidate the data into a single spreadsheet or accounting tool. This is the foundation for both methods, and it is also useful for reconciling your records with exchange statements. A common mistake is to rely solely on exchange-provided reports, which may not include all transactions, such as those from decentralized exchanges or gifts. Therefore, maintain your own independent log. This log will help you answer questions like: What was the average cost on the day of a specific sale? Did a large purchase later in the year affect the annual average? Without these details, you are guessing, and guessing is not a strategy.

Identifying Unanswered Questions Early

Before you commit to a method, you need to identify the questions that your records alone cannot answer. For example, what happens if you received crypto as payment for goods or services? The acquisition cost is the fair market value at the time of receipt, but you need a reliable source for that value. Similarly, if you transferred crypto between your own wallets, does that count as a disposal? In many cases, moving your own crypto between your own wallets is not a taxable event, but you need to document the transfer to prove it. Another common question is how to handle fees. Are fees added to the acquisition cost or deducted from the disposal proceeds? The answer can affect your average. Also, consider what happens if you hold the same type of crypto in multiple wallets. For the total average method, you aggregate all holdings of that type, but for the moving average, you might need to track each wallet separately if you dispose from specific wallets. These are not trivial points. The best approach is to write down every assumption you make and every question you cannot answer. Then, seek professional advice for those specific issues. Do not assume that a default answer is correct. For instance, the default method is total average, but that does not mean it is the best for your situation. By identifying these questions early, you avoid surprises at filing time.

Reconciling Sources and Documenting Assumptions

Once you have your records, you must reconcile them with external sources. This means comparing your transaction log with exchange statements, bank records, and any other documentation. Discrepancies can arise from timing differences, fees not recorded, or missing transactions. For each discrepancy, investigate and resolve it. For example, if an exchange statement shows a trade that you did not record, determine whether it was a legitimate trade or an error. If it was a legitimate trade, add it to your log. If it was an error, contact the exchange to correct the statement. After reconciliation, document every assumption you made. For instance, if you used a specific exchange rate for a transaction, note the source and the date. If you treated a transfer as non-taxable, write down why. This documentation is crucial if you are ever audited. It shows that you made a good-faith effort to comply. It also helps you if you need to change your method later, because you can show the basis for your original calculations. A practical way to document is to keep a separate file or section in your spreadsheet for assumptions. For each assumption, include the date, the reason, and any supporting evidence. This file becomes your reference point for future years, and it makes it easier to answer questions from your tax preparer or the tax office.

Reviewing Before You File or Close

Before you file your tax return or close your books for the year, do a thorough review of your calculations. This is your last chance to catch errors. Start by checking that you have included all transactions. Compare your transaction count with your exchange reports. Then, verify that your average cost calculations are correct. For the total average method, ensure that you have included all acquisitions for the year and that the average is computed correctly. For the moving average, check that each disposal uses the correct average at that point in time. A simple way to test is to calculate the total cost of all acquisitions and the total proceeds from all disposals. The difference should equal your net gain or loss before considering other factors. If the numbers do not match, investigate. Also, review your assumptions. Did you treat a transaction correctly? Did you use the right exchange rate? Finally, consider whether your method choice is still appropriate. If your trading pattern changed during the year, the method you elected might not be optimal. However, you cannot change it retroactively, so this review is about ensuring accuracy, not about optimizing after the fact. If you are unsure about any aspect, consult a qualified professional before filing. It is better to ask now than to face an inquiry later.

Knowing When to Seek a Qualified Professional

Crypto tax is complex, and the rules can change. While this article provides general guidance, it is not a substitute for professional advice. You should seek a qualified tax professional if you have a high volume of transactions, if you trade across multiple jurisdictions, if you have received crypto as income, or if you are unsure about any aspect of your tax obligations. A professional can help you choose the right method, prepare the necessary notifications, and ensure that your records meet the required standards. They can also help you if you need to change your method, as the process involves filing an application and obtaining approval. The cost of professional advice is often less than the cost of a mistake. For example, if you incorrectly apply the moving average method, you might underpay or overpay your tax, leading to penalties or missed savings. A professional can also help you understand the implications of new regulations or court decisions. Remember, the default method is total average, but that does not mean it is the best for you. A professional can analyze your trading pattern and recommend the method that minimizes your tax liability while remaining compliant. Finally, if you are ever audited, having a professional on your side can make the process less stressful. They can represent you and ensure that your rights are protected. So, do not hesitate to seek help when you need it.