Most homeowners in the South Suburbs know roughly what they paid for their home. Very few know their adjusted cost basis. That gap matters. When you sell, the IRS does not tax what you receive. It taxes what you gained. For anyone planning a South Suburbs home sale after years of ownership, understanding adjusted cost basis could mean the difference between a significant tax bill and almost none at all.
What Is Cost Basis?
Your cost basis starts simply. It is what you originally paid for your home, including the purchase price and certain closing costs you paid at settlement. According to IRS Publication 523, settlement costs you can include in your basis are transfer taxes, title insurance, and certain legal fees. The purchase price alone is your starting point, but it rarely stays there.
What Makes It “Adjusted”?
Over the years, your basis adjusts. Capital improvements increase it. Certain events decrease it. The result is your adjusted cost basis, and it is the figure the IRS uses when calculating how much profit you actually made on the sale.
According to Nolo’s guide to home tax basis, your adjusted basis is your original cost plus capital improvements, minus any casualty loss payments you received from insurance or other reductions. Understanding this calculation before you sell puts you in a much stronger position to plan effectively.
What Counts as a Capital Improvement?
This is where many homeowners leave money on the table. A capital improvement is a permanent upgrade. It must add value, extend the home’s useful life, or adapt it to a new use. According to American Tax Service’s 2026 guide to home improvements and capital gains, qualifying improvements include items such as a new roof, an added room or bathroom, a kitchen renovation, central air conditioning, new windows, a finished basement, and landscaping that permanently improves the property.
Routine repairs do not qualify. Painting a room, fixing a leaky faucet, or replacing a broken appliance generally does not increase your basis. However, if that painting was part of a larger renovation project, it may qualify as part of the overall cost of improvements. The distinction matters and is worth discussing with a CPA.
The Simple Math — How It Actually Works
Here is the clearest way to see it:
Original Price + Major Improvements = Adjusted Cost Basis
Think of your adjusted cost basis as your total investment in the home. The higher that number, the less profit you appear to make on paper, which means less tax owed. Here is a simple example:
You bought your home for $200,000. Over the years, you added a new roof ($20,000), renovated the kitchen ($30,000), and built a deck ($10,000). Your adjusted cost basis is now $260,000.
When you sell for $500,000, the IRS subtracts $260,000, not $200,000. Your taxable gain becomes $240,000. Not $300,000. Those three improvements saved you from being taxed on $60,000 of profit.
One rule to remember. The IRS draws a clear line between improvements and repairs. An improvement adds value or extends the life of the home, such as a new roof, central air, an added bathroom, or a kitchen renovation. A repair fixes something that broke, for example, a leaky faucet, a broken window, or a coat of paint. Repairs do not increase your basis. Improvements do. Keep every receipt for every major project. For homeowners who have owned their South Suburbs home for decades, those receipts can be worth thousands of dollars in tax savings.
Why This Matters in Real Numbers
Here is a straightforward example. Say you purchased your South Suburbs home for $180,000 thirty years ago. Over those decades, you added a bathroom for $25,000, replaced the roof for $18,000, renovated the kitchen for $35,000, and added central air for $12,000. That is $90,000 in capital improvements.
Your adjusted cost basis is now $270,000. If you sell for $520,000, your gain is $250,000, not $340,000. For a single filer, the Section 121 exclusion covers up to $250,000 of gain on a primary residence. In this example, the improvements effectively bring your taxable gain to zero. Without them factored in, you may have assumed you had a taxable gain and either worried unnecessarily or failed to plan properly.
As TurboTax explains, your adjusted cost basis is your total purchase price plus qualifying improvements. Subtract that from your sale price to find your actual gain.
What Records Do You Need?
Documentation is essential. The IRS expects receipts, contractor invoices, permit records, and bank statements. According to IRS Publication 523, keep these records for as long as you own the home and for at least three years after the sale. If older receipts are missing, permit records filed with your local municipality may help. A CPA can help you reconstruct what is recoverable.
If you no longer have receipts for older work, do not assume all is lost. Permit records filed with your local municipality can sometimes serve as documentation. A CPA with real estate experience can help you reconstruct what is recoverable and make the strongest case for your adjusted basis.
The Step-Up in Basis for Inherited Homes
If you inherited your home rather than purchased it, a different rule applies. The step-up in basis resets your cost basis to the fair market value of the property at the time you inherited it. This means decades of appreciation during the previous owner’s lifetime simply disappear from the tax calculation. In many cases, heirs who sell an inherited home shortly after receiving it owe little or no capital gains tax at all, regardless of how much the property appreciated over the years.
This is one of the most valuable and least understood provisions in the tax code for homeowners over 50. Whether you are dealing with your own home or one you have inherited, understanding the basis rules before any decisions are made is essential.
What to Do Before You Sell
Before listing your South Suburbs home, take three steps. First, gather every receipt, invoice, and permit record for home improvements made during your ownership. Second, schedule a conversation with a CPA or tax advisor who has real estate experience. Third, talk to your SRES® about timing. The year you sell can affect your overall tax picture, particularly if a large gain pushes you into a higher income bracket or triggers IRMAA Medicare premium increases.
For a broader look at the financial side of selling your home, the free one-page guide What to Expect When You Meet With a Financial Advisor walks you through exactly how to prepare for that first professional conversation.
My goal is simple. I want to make sure you feel informed, empowered, and supported at every stage of this process. That is why I put together a free resource library packed with guides covering everything from downsizing and aging in place to senior living options and financial planning. And if you would like to understand more about what an SRES® does and why it matters for homeowners over 50, the Homeowners 50+ page is a good place to start.
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This blog is for educational purposes only and does not constitute tax, legal, or financial advice. Every homeowner’s situation is unique. Please consult a qualified CPA, tax advisor, or estate attorney before making any decisions related to the sale of your home.
If you’re starting to think about what comes next, you don’t have to figure it out on your own. Sometimes it helps just to talk things through.
You can always take the next step at your own pace, with no pressure and no expectations. I’m always happy to help you get a clearer picture of your options.
Michelle Williams is a REALTOR® and SRES® serving Chicago and the South Suburbs, helping homeowners 50+ make confident decisions about their next move.