The IRS knows your cost basis primarily through mandatory reporting from financial institutions on Form 1099-B for stocks, bonds, and mutual funds purchased in 2011 or later. Brokers report the purchase price, fees, and adjustments (like wash sales) directly to the IRS, allowing them to verify gains or losses when you sell.
How Does the IRS Verify Cost Basis in Real Estate? In real estate transactions, the Internal Revenue Service (IRS) can verify the cost basis by looking at the closing statement of when the property was purchased, or any other legal documents associated with the property, such as tax statements.
The IRS expects taxpayers to keep the original documentation for capital assets, such as real estate and investments. It uses these documents, along with third-party records, bank statements and published market data, to verify the cost basis of assets.
The bottom line is that the IRS expects you to maintain records that identify the cost basis of your securities. If you don't have adequate records, you might have to rely on the cost basis that your brokerage firm reports—or you may be required to treat the cost basis as zero, which could mean owing more in taxes.
Thanks to a law passed in 2008, taxpayers receive help keeping track of their tax basis. The law requires brokers to track the basis of specified securities (including stocks and mutual fund shares) purchased in 2011 and later years and report the basis amounts to investors (and the IRS) when the securities are sold.
What happens if no cost basis is reported for a noncovered sale? Without cost basis, the IRS may treat the entire sale amount as a gain, which may increase reported income from sales.
But the chances of being audited are actually very low for most individuals. Recent IRS data shows the IRS examined 0.40% of individual returns filed and 0.66% of corporation returns filed. Most of the IRS's focus is on large businesses and high-income earners.
Will the IRS catch a missing 1099? The IRS knows about any income that gets reported on a 1099, even if you forgot to include it on your tax return. This is because a business that sends you a Form 1099 also reports the information to the IRS.
Proving Your Cost Basis
Homeowners should keep good records of improvements they have made to a house, including keeping copies of all receipts and purchase orders. If a joint owner of property dies, you should get the property appraised to show the value at the time it is stepped up in basis.
If capital gains from the sale of assets such as stocks, bonds, or property are not disclosed, the following consequences may occur: Interest on Unpaid Taxes: If the capital gains result in taxable income and are not reported, the tax authorities may impose interest on unpaid taxes under Section 234A, 234B, and 234C.
On a $100,000 capital gain, you'll likely pay 15% for long-term gains, resulting in about $15,000 in federal tax (plus potential state tax), but it could be 0% or 20% depending on your total taxable income and filing status, while short-term gains are taxed as ordinary income (potentially 22-24%).
In real estate dealings, the IRS can confirm the cost basis by examining the closing statement from the property's purchase or any relevant legal documents connected to the property, such as tax statements.
The IRS $600 rule refers to a change in reporting requirements for third-party payment apps (like Venmo, PayPal) for taxable income from goods and services, where platforms must send a Form 1099-K if you receive over $600 in a year, intended to capture gig economy/side hustle income, though delays and phased implementation have adjusted the timeline, with current rules for 2024 using a higher threshold ($5,000) before fully phasing to $600 for future years, but remember all taxable income, regardless of form, must always be reported.
If you lost or didn't keep records to determine your basis in securities, contact your broker for help. If you receive a Form 1099-B (or substitute statement), your broker may have reported your basis for these securities in box 1e.
The 20% rule for capital gains refers to the highest federal tax rate for long-term capital gains, applying to higher income brackets when you sell investments (stocks, real estate) held for over a year, with lower rates of 0% and 15% for lower incomes, and even higher rates for special assets like collectibles. This rate kicks in for single filers earning over approximately $492,300 (2024) or $533,401 (2025), and higher for joint filers, making holding assets over a year a key tax strategy.
If the cost basis amount reported on Form 1099-B does not match your adjusted cost basis per your records, you will include adjustment code B on your tax return. Compensation income reported on Form W-2 is likely not included in your cost basis on Form 1099-B and will require an adjustment amount using code B.
Since the law passed, brokers are required to report cost basis information on Form 1099-B and to the IRS after the sale of certain securities, including stocks, bonds, options, exchange-traded funds (ETFs), and mutual funds. Mandatory reporting was rolled out in phases between 2011 and 2016: January 1, 2011: Equities.
No, the IRS doesn't catch every instance of unreported income, but their advanced data-matching systems catch most discrepancies involving third-party reporting (like W-2s, 1099s for freelance/interest/dividends) through automated checks, leading to CP2000 notices and potential penalties if missed; however, cash income, crypto, or lifestyle mismatches can also trigger scrutiny, though it's less certain than reported income, and high-income non-filers are a current focus.
The biggest tax mistakes people make include filing late, math errors, incorrect personal info (like Social Security numbers), forgetting deductions/credits (like EITC), misreporting income, not signing forms, and making errors with bank details for direct deposit, all leading to delays, penalties, or missed savings, with using tax software or professionals helping avoid these common pitfalls.
Will the IRS Catch a Missing 1099? 2026 Guide. The IRS can catch a missing 1099 form as they receive copies from payers. If you forget to report it, you risk penalties and interest on unpaid taxes.
Not reporting all of your income is an easy-to-avoid red flag that can lead to an audit. Taking excessive business tax deductions and mixing business and personal expenses can lead to an audit. The IRS mostly audits tax returns of those earning more than $200,000 and corporations with more than $10 million in assets.