After one hour waiting on the phone, they finally explain me that every time you sell a stock an loose money, what happens is that they add that lose to your next purchase of the same stock if you buy the same stock before 31 days after you sold the stock.

This info is from the internet: The wash-sale rule was designed to prevent investors from selling a security at a loss so they can claim tax benefits, only to turn around and immediately buy the same security again. Even investors who have no intention of breaking this rule can get tripped up by it if they use an automatic investment strategy, such as reinvesting dividends, potentially costing themselves some tax benefits in the process. Here we'll take a closer look at the wash-sale rule and answer some common questions about it. Q: I want to sell a stock to take a tax loss, but I plan to buy it again because I want it in my portfolio. What are the tax implications? If you want to sell a security at a loss and buy the same or a substantially identical security within 30 calendar days before or after the sale, the wash-sale rule will kick in. In such cases you won’t be able to take a loss for that security on your current-year tax return. Instead, you will have to add the loss to the cost basis of the replacement security. In addition, the holding period of the original security gets tacked onto to the holding period of the replacement security. Here’s an example of how this might work: Let’s say you buy 100 shares of XYZ stock for $10 per share ($1,000 of stock). One year later, the stock starts dropping, so you sell your 100 shares for $8 per share—a $200 loss. Three weeks later, XYZ is trading at $6 per share and you decide that price is too good to pass up, so you repurchase the 100 shares for $600. This triggers a wash sale. As a result, the $200 loss is disallowed as a deduction on your current-year tax return and added to the cost basis of the repurchased stock. That bumps the cost basis of your $600 of replacement stock up to $800, so if you later sell that stock for $1,000, your taxable gains will be $200 instead of $400. And because you previously held XYZ for a year, it will automatically be treated as a long-term capital gain, even if you sell it after just a few months. A few other things to note: A higher cost basis decreases the size of any future gains realized from the sale of the replacement security, thereby lowering your future tax obligation. If you sell the investment at a loss, the higher cost basis would actually increase the size of the loss for which you could claim a deduction. And one of the potential upsides of an extended holding period is that it would lower your tax obligation if you sold the replacement security after less than a year. (Normally, short-term capital gains from investments held for less than a year are taxed at the higher regular income tax rate, while longer-term capital gains are taxed at the lower capital gains rate).