Importing the 1099 is not the problem, a lot of people are not using form 8949 with the corrected wash sales cost basis. This ends up costing them a bundle.
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Source: GreenTraderTax
Most active traders make serious errors on income tax returns, whether they self-prepare or engage a local accountant. Many miss out on trader tax benefits and overpay on their taxes. The cost ranges from $5,000 to hundreds of thousands of dollars.
1. Mistakenly believing you can rely on securities Form 1099-B:
Most preparers rely on broker Form 1099-B for tax reporting. There’s a problem with wash sales. A wash sale loss is tax-deferred when you buy back a security position 30 days before or after making a sale at a loss.
Here’s the problem with wash sales reported on the 1099-B: IRS rules for brokers are simple, and most people do not realize that IRS rules for taxpayers are different and more complex. Tax preparers choose to play ignorant and import 1099-B, so it’s easy to reconcile Form 8949 with 1099-B. That means they are using broker rules and willfully disregarding Section 1091 rules for taxpayers. They should use trade accounting software that is compliant with taxpayer rules.
Broker rules base wash sales on identical positions, per account. Taxpayer rules base wash sales on substantially identical positions, across all accounts, including IRAs. A broker does not calculate a wash sale on Apple equity vs. Apple options because they are not identical symbols, but taxpayers must do so because they are substantially identical positions.
With education, traders can avoid wash sale losses. That is better than ignoring taxpayer rules and playing the audit lottery with the IRS.
2. Messing up Form 8949 cost-basis reporting:
The IRS requires reporting each securities trade on Form 8949 with the description, dates acquired and sold, proceeds, cost basis, code, adjustments, and gain or loss.
The primary adjustment is for wash sales. Other cost-basis adjustments include corporate actions (stock splits and reinvested dividends), inherited positions, gifts, and transfers from other accounts. Taxpayers often use incorrect amounts for these items.
There is one scenario where a taxpayer can solely rely on a 1099-B and skip filing Form 8949 by entering 1099-B amounts on Schedule D: when the taxpayer has only one brokerage account and trades equities only with no trading in equity options, which are substantially identical positions. Plus, the taxpayer must not have any wash sale loss or other adjustments.
However, if you trade options and equities, which are substantially identical positions, and/or you have multiple brokerage accounts, including IRAs, then you need trade accounting software that’s compliant with Section 1091 to generate Form 8949. Most software available through brokerage websites are not compliant with taxpayer rules in Section 1091. Download the original trade history from your broker’s website into a compliant program to generate Form 8949 or Form 4797 with Section 475.
https://greentradertax.com/these-tax-errors-will-cost-professional-traders-dearly/