My Brokerage statement shows “Adjusted due to previous wash sale disallowed loss” what does this mean?
Well it would appear that you had a wash sale that canceled out a loss position.  Without seeing the entire report, I couldn't tell you exactly what was happening or how you triggered § 1091.  But just from the excerpted images, it appears as though your purchase of stock was layered into multiple tranches - perhaps you acquired more of the stock in the 61-day period than you sold (possibly because of a prior holding).   If in the 61-day period around the sale of stock (30 days before and 30 days after), you also acquire the same stock (including by contract or option), then it washes out your loss.  If you held your stock for a while, then in a 61-day period bought more, and sold some, then any loss would be washed out by the acquisition.  Of course it is also a wash sale if your purchase of the stock follows your sale, rather than precedes it.  Your disallowed loss goes into the basis of your stock holding, so will be meaningful when you do have a true economic sale of that stock. From IRS Pub 550: A wash sale occurs when you sell or trade stock or securities at a loss and within 30 days before or after the sale you: Buy substantially identical stock or securities, Acquire substantially identical stock or securities in a fully taxable trade, Acquire a contract or option to buy substantially identical stock or securities, or Acquire substantially identical stock for your individual retirement account (IRA) or Roth IRA. If you sell stock and your spouse or a corporation you control buys substantially identical stock, you also have a wash sale. Looking at your excerpted account images, we can see a number of positions sold at a loss (sale proceeds less than basis) but each one is adjusted to a zero loss.  I suspect the fuller picture of your account history and portfolio will show a more complicated and longer history with this particular stock.  That is likely the source of the wash sale disallowed loss notations. You might be able to confirm that all the added numbers are appearing in your current basis in this stock (or were reflected upon your final exit from the stock). "Summary of accepted answer: Your ""loss"" will not count as a loss (to the IRS).  Which means no tax deduction for a ""short-term capital loss"" (on that sale). Instead, the IRS simply pretends like you had paid less for the stock to begin with."
Calculating and adjusting cost basis accurately is a daunting task, but there is a (paid) online tool, NetBasis, which will automatically calculate and adjust your cost basis.  It is used by brokerage firms and Fortune 500 companies and is available to the public.  Go to netbasis.com. All you need are the purchase and sale dates and shares of the stock or mutual fund and the system has the rest of the information, such as corporate actions (splits, spin-offs, etc), pricing, and dividends and it also will apply the appropriate IRS rules for inherited and gifted shares. The regulation also gives investors the option to choose calculation methods.  Not only does NetBasis automatically calculate the method you choose, it will also give the results for all options and allow you to choose the best result. NetBasis also provides you with detailed supporting documentation which shows all of the calculations and the adjustments in chronological order. NetBasis has data going back as far as 1925, so it will accurately calculate cost basis for your old American Telegraph and Telephone shares. NetBasis also handles complex investment scenarios such as wash sales, short sales, return of capital, etc. Moderator's note: Disclosure: The answerer's profile indicates they are affiliated with NetBasis. My employer matches 1 to 1 up to 6% of pay. They also toss in 3, 4 or 5 percent of your annual salary depending on your age and years of service. The self-directed brokerage account option costs $20 per quarter. That account only allows buying and selling of stock, no short sales and no options. The commissions are $12.99 per trade, plus $0.01 per share over 1000 shares. I feel that's a little high for what I'm getting. I'm considering 401k loans to invest more profitably outside of the 401k, specifically using options. Contrary to what others have said, I feel that limited options trading (the sale cash secured puts and spreads) can be much safer than buying and selling of stock. I have inquired about options trading in this account, since the trustee's system shows options right on the menus, but they are all disabled. I was told that the employer decided against enabling options trading due to the perceived risks. This is really an extended comment on the last paragraph of @BenMiller's answer. When (the manager of) a mutual fund sells securities that the fund holds for a profit, or receives dividends (stock dividends, bond interest, etc.), the fund has the option of paying taxes on that money (at corporate rates) and distributing the rest to shareholders in the fund, or passing on the entire amount (categorized as dividends, qualified dividends, net short-term capital gains, and net long-term capital gains) to the shareholders who then pay taxes on the money that they receive at their own respective tax rates. (If the net gains are negative, i.e. losses, they are not passed on to the shareholders. See the last paragraph below).  A shareholder doesn't have to reinvest the distribution amount into the mutual fund: the option of receiving the money as cash always exists, as does the option of investing the distribution into a different mutual fund in the same family, e.g. invest the distributions from Vanguard's S&P 500 Index Fund into Vanguard's Total Bond Index Fund (and/or vice versa). This last can be done without needing a brokerage account, but doing it across fund families will require the money to transit through a brokerage account or a personal account. Such cross-transfers can be helpful in reducing the amounts of money being transferred in re-balancing asset allocations as is recommended be done once or twice a year. Those investing in load funds instead of no-load funds should keep in mind that several load funds waive the load for re-investment of distributions but some funds don't: the sales charge for the reinvestment is pure profit for the fund if the fund was purchased directly or passed on to the brokerage if the fund was purchased through a brokerage account. As Ben points out, a shareholder in a mutual fund must pay taxes (in the appropriate categories) on the distributions  from the fund even though no actual cash has been received because the entire distribution has been reinvested. It is worth keeping in mind that when the mutual fund declares a distribution (say $1.22 a share), the Net Asset Value per share drops by the same amount (assuming no change in the prices of the securities that the fund holds) and the new shares issued are at this lower price. That is, there is no change in the value of the investment: if you had $10,000 in the fund the day before the distribution was declared, you still have $10,000 after the distribution is declared but you own more shares in the fund than you had previously. (In actuality, the new shares appear in your account a couple of days later, not immediately when the distribution is declared).  In short, a distribution  from a mutual fund that is re-invested leads to no change in your net assets, but does increase your tax liability. Ditto for a distribution that is taken as cash or re-invested elsewhere. As a final remark, net capital losses inside a mutual fund are not distributed to shareholders but are retained within the fund to be written off against future capital gains. See also this previous answer  or this one. From the IRS Section 1091. Loss from Wash Sales of Stock or Securities  Section 1091(a) provides that in the case of any loss claimed to have been sustained from any sale or other disposition of shares of stock or securities where it appears that, within a period beginning 30 days before the date of such sale or disposition and ending 30 days after such date, the taxpayer has acquired (by purchase or by an exchange on which the entire amount of gain or loss was recognized by law),or has entered into a contract or option so to acquire, substantially identical stock or 3 securities, then no deduction shall be allowed under § 165 The document is not long, 4 pages, and should be read to see the intent. It's tough to choose the one snippet, but the conclusion is this is the definitive response to that question.  A purchase within an IRA or other retirement account can create a wash sale if such a purchase would be a wash sale otherwise, i.e. the fact that it's a retirement account doesn't avoid wash rules. "The IRS has been particularly vague about the ""substantially identical"" investment part of the wash rule.  Many brokers, Schwab for instance, say that only identical CUSIPs (exactly the same ETF) matter for the wash rule in their internal calculations, but warn that the IRS might consider two ETFs over the same index to be substantially identical.  In your case, the broker has chosen to call these a wash despite even having different underlying indices.  Talking to the broker is the first step as they will report it to the IRS.  Though technically you have the final say in your taxes about the cost basis,  discussing this with the IRS could be rather painful. First though it is probably worth checking with your broker about exactly what happened.  There are other wash sale triggers that frequently trip people up that may have been in play here." Underwriting manager here. It's not a big deal. Call your processor or loan officer tomorrow to make sure it's been cleared. My guess is that the underwriter or loan officer noted the discrepancy and corrected it in their systems. You'll have to sign a updated 1003 and 4506T at closing with correct info.  In other words...no biggie, no worries. Not a show stopper at all. Interesting.  How would they account for it? Monthly? And if so do they modify the cost basis for each lot for the month and then restate?   It's hard to imagine they do that.   I have a million questions regarding this topic do you know where in the regs it is covered? IESC has a one-time, non-repeatable event in its operating income stream.  It magnifies operating income by about a factor of five.  It impacts both the numerator and the denominator.  Without knowing exactly how the adjustments are made it would take too much work for me to calculate it exactly, but I did get close to their number using a relatively crude adjustment rule. Basically, Yahoo is excluding one-time events from its definitions since, although they are classified as operating events, they distort the financial record.  I teach securities analysis and have done it as a profession.  If I had to choose between Yahoo and Marketwatch, at least for this security, I would clearly choose Yahoo.