The moment you sell crypto at a profit, in Israel this is considered a taxable event. It's important to understand what this means before year-end, not after you've already made dozens of transactions without documenting anything.
In most cases, capital gains from crypto are taxed like capital gains on another asset, at the relevant tax rate in effect at the time. It's important to keep organized documentation of every transaction: purchase date, purchase price, sale date, sale price, and fees paid along the way. The difference between the purchase cost and the sale price is the basis for calculating the taxable profit.
Even converting from one cryptocurrency to another (for example, Bitcoin to Ethereum) can be considered a taxable event, because in practice you "sold" one asset and bought another, even if it didn't pass through shekels. Therefore, it's worth documenting these types of transactions too, not just conversions to fiat money.
It's highly recommended to get help from an accountant familiar with the field, and not try to "guess" yourself, especially if you have a complex trading history. Correct and timely reporting saves you unnecessary headaches, and interest and linkage charges on late payment.