For many homeowners, receipts for renovations, repairs, and upgrades tend to disappear into drawers, old email accounts, or forgotten contractor portals. At the time, that may not seem like a serious problem. After all, the project is finished, the kitchen looks better, the roof has been replaced, and the home’s value has hopefully increased.

But from a tax perspective, those records may matter years, or even decades, later.

The reason is basis. A homeowner’s basis in a property is generally the starting point for calculating taxable gain when the home is sold. The higher the adjusted basis, the lower the potential capital gain. And with home values having risen significantly in many markets, basis documentation is no longer a technical issue that only affects investors or ultra-high-net-worth families. It is becoming a mainstream tax planning concern.

The IRS generally allows homeowners to add the cost of qualifying improvements to the basis of their home. These are not ordinary repairs or maintenance items, but expenditures that add value to the property, substantially prolong its useful life, or adapt it to a new use. Examples may include additions, major renovations, new systems, roof replacements, certain landscaping projects, and other capital improvements. That distinction can become financially meaningful when the home is sold.

The home sale exclusion helps, but it may not be enough

Many homeowners assume the home sale exclusion will eliminate any federal capital gains tax when they sell. Under current federal rules, a taxpayer may be able to exclude up to $250,000 of gain from the sale of a principal residence, or up to $500,000 for certain married couples filing jointly, if they meet the ownership and use requirements.

For years, that exclusion was large enough to protect many homeowners from federal capital gains tax. But the exclusion amounts are not indexed for inflation. In high-appreciation markets, a couple who bought a home decades ago may now have unrealized gain well above $500,000. A single homeowner, surviving spouse, divorced homeowner, or unmarried co-owner may have even less protection relative to the appreciation in the property.

That is where basis documentation becomes critical.

Consider a couple who purchased a home for $400,000 and later sells it for $1.2 million. At first glance, the gain appears to be $800,000. If they qualify for the full $500,000 exclusion, they may still have $300,000 of potentially taxable gain before considering selling costs and other adjustments.

Now assume they can document $175,000 of qualifying capital improvements over the years: a major kitchen renovation, a new roof, upgraded HVAC, a room addition, and a new deck. Those improvements may increase their adjusted basis and reduce the potential taxable gain. Without documentation, however, they may have difficulty substantiating those costs if questioned.

The tax result may depend not only on what was spent, but on what can be proven.

Improvements versus repairs: the recordkeeping trap

One of the most common mistakes homeowners make is assuming every home-related expense increases basis. It does not.

Routine repairs generally do not increase basis. Painting a room, fixing a leak, replacing a broken windowpane, or servicing an HVAC unit may be necessary, but these costs are usually treated as maintenance rather than capital improvements. By contrast, replacing the entire HVAC system, adding a bathroom, installing new plumbing, building an addition, or replacing the roof may be capital improvements that can increase basis. 

The general standard is whether the expenditure adds value to the home, substantially prolongs the property’s useful life, or adapts the property to a new or different use. In addition, taxpayers may need to reduce basis for certain items, such as depreciation allowed for business or rental use, casualty loss deductions, or certain credits. 

The practical problem is that homeowners often do not categorize these expenses at the time they occur. A folder labeled “house stuff” may contain a mix of repairs, maintenance, capital improvements, appliance purchases, and contractor invoices. Years later, trying to reconstruct what happened can be difficult.

The best practice is to create a permanent home basis file. That file should include contractor invoices, proof of payment, permits, settlement statements, architectural plans, before-and-after photos, insurance claim documentation, and a simple spreadsheet summarizing the date, vendor, project description, amount paid, and whether the cost appears to be a capital improvement.

Basis also matters for inherited homes

Basis is not only relevant when homeowners sell during life. It is also central to estate and inheritance planning.

When a person inherits property, the tax basis is often adjusted to the property’s fair market value at the date of the decedent’s death, commonly referred to as a “step-up” in basis. The IRS notes that inherited property valuation may need to be consistent with the value finally determined for federal estate tax purposes in certain circumstances.

This rule can significantly reduce capital gains tax exposure for heirs. However, it does not eliminate the need for documentation. Families may still need records to establish the value of the home at death, identify post-death improvements, allocate basis among multiple heirs, or support the basis used when the inherited property is later sold.

For example, if children inherit a home and sell it shortly after death, the date-of-death value may be the most important basis figure. But if they hold the property for several years, rent it out, renovate it, or convert it to a vacation home, new basis adjustments may arise. Without clear records, heirs may struggle to determine the correct taxable gain.

This can become especially complicated in blended families, jointly owned homes, community property states, trusts, or situations where one spouse dies years before the surviving spouse sells the property. In some cases, only a portion of the property receives a basis adjustment at death. In others, the entire property may be adjusted, depending on ownership structure and applicable state law.

Rising home values have raised the stakes

For decades, many homeowners could afford to be casual about basis records because their gains were either modest or fully sheltered by the home sale exclusion. That assumption is less safe today.

Longtime owners in appreciating markets may be sitting on gains that far exceed the federal exclusion. Retirees downsizing from homes purchased 20, 30, or 40 years ago may discover that their home is one of their largest appreciated assets. Widows, widowers, and single taxpayers may face particular exposure because the $250,000 exclusion can be quickly exceeded in expensive markets. Families inheriting property may also face disputes or tax uncertainty if no one preserved records of improvements, appraisals, or ownership changes.

The issue is not just federal tax. State income taxes may also apply, and some states do not follow every federal rule in the same way. Local real estate transfer taxes, depreciation recapture for rental use, home office issues, casualty losses, and prior energy credits can further complicate the calculation.

In other words, the sale of a home is not always a simple personal transaction. For many families, it is a major tax event.

What homeowners should track

Homeowners should retain records for any project that materially improves the property, extends its life, or changes its use. This may include additions, kitchen and bathroom remodels, new roofing, new windows, electrical upgrades, plumbing replacements, HVAC systems, finished basements, decks, patios, driveways, fencing, major landscaping, accessibility modifications, and certain energy improvements.

They should also retain closing documents from the original purchase and any refinancing or later sale, including settlement statements and records of buying or selling costs. Selling expenses can also affect the gain calculation, so broker commissions, legal fees, transfer taxes, staging costs, and other transaction-related expenses should be preserved.

For inherited homes, families should obtain and retain a qualified appraisal or other support for fair market value as of the date of death. They should also document any improvements made after inheritance and any rental or business use that may affect basis.

A simple spreadsheet can be enough if it is supported by underlying records. The goal is not to create unnecessary complexity. The goal is to make sure that, when the property is sold, gifted, transferred, or inherited, the taxpayer and advisor can support the adjusted basis used for tax purposes. 

Why this matters even if you are not planning to sell

Homeowners often view basis tracking as something to address only when a sale is imminent. However, there are many reasons a homeowner may need reliable basis information even if selling is not currently part of the plan. A job change, relocation, divorce, death of a spouse, family transition, liquidity need, health event, or change in estate planning objectives can turn a long-held residence into an active planning issue with little notice. In those moments, having records readily available can make the difference between informed decision-making and a rushed reconstruction effort.

Maintaining a running total of capital improvements can also help advisors evaluate whether the home sale exclusion is likely to cover the potential gain. If a homeowner is considering selling, downsizing, transferring the home, converting it to rental use, or retaining it for heirs, current basis information provides a clearer picture of the tax consequences. 

This doesn’t need to be complicated. You can periodically share a running list of improvements with your CPA or tax advisor as part of your annual tax process. That approach can be far more efficient than trying to reconstruct decades of home projects after the fact, when records are missing, contractors are no longer available, or family members remember the details differently.

The bottom line

Home improvement records may not feel like tax documents when a project is underway. But years later, they can determine how much gain is taxable when a home is sold or inherited property is later disposed of.

With home values substantially higher in many parts of the country, homeowners should not assume the home sale exclusion will eliminate the issue. Basis matters. Documentation matters. And the absence of records can turn legitimate tax savings into missed opportunities.

Homeowners should begin maintaining a permanent basis file now, especially if they have owned their home for many years or have completed significant improvements. This is useful even for those who have no immediate plans to sell, because life events, family changes, and planning opportunities can arise unexpectedly. 

If you’re considering selling, gifting, transferring, or inheriting a home, please contact one of our advisors. We can help determine the property’s adjusted basis, identify available exclusions, and evaluate the capital gains consequences before important decisions are made.