Tax basis measures an owner's tax investment in property or an entity interest. Learn initial and adjusted basis, sale gain, depreciation and records.
Tax basis is the amount assigned to property or an ownership interest for tax calculations. It often begins with cost, but the starting rule depends on how the asset was acquired. Later events can increase or decrease basis.
Basis affects gain or loss on a sale, depreciation and amortization deductions, casualty calculations, tax-free recovery of investment, loss limitations, and the treatment of partnership or S-corporation distributions.
A useful framework is:
Initial basis + basis increases − basis decreases = adjusted basis
Possible increases include capital improvements, additional capital contributions, and certain acquisition costs. Possible decreases include depreciation allowed or allowable, casualty reimbursements, return-of-capital distributions, and other tax adjustments.
The correct additions and reductions depend on the asset or ownership interest. Tax basis should not be estimated solely from current market value or a balance-sheet number.
Assume a business buys equipment for $40,000 and pays $2,000 of qualifying delivery and installation costs. Initial basis is $42,000.
Over time, the business claims $17,000 of depreciation. Ignoring other adjustments:
$42,000 initial basis − $17,000 depreciation = $25,000 adjusted basis
If the equipment is sold for $30,000, the simplified realized gain is:
$30,000 amount realized − $25,000 adjusted basis = $5,000 gain
The character of the gain can involve depreciation-recapture rules. The example shows why subtracting only the original purchase price would be wrong after depreciation.
Tax basis is the broad concept. Cost basis commonly describes the starting basis of purchased property: purchase price plus qualifying acquisition costs.
Adjusted basis is the basis after increases and decreases. When property is sold, adjusted basis — not necessarily original cost — is generally used to calculate gain or loss.
These terms overlap in ordinary conversation, but the distinctions matter when applying specific tax rules to gifts, inheritance, depreciation, distributions, and entity interests.
Basis generally begins with cost, including qualifying amounts paid to acquire and place the property in service. Financing does not usually reduce basis merely because money was borrowed.
Gift basis often begins with the donor's adjusted basis, but fair market value at the date of the gift can matter when property has declined in value. Separate gain and loss basis rules can produce no recognized gain or loss in the middle range. Gift tax paid can also affect basis in limited circumstances.
Inherited-property basis is generally tied to fair market value at the date of death or an alternate valuation date when properly elected. Important exceptions apply, including income in respect of a decedent and certain property reacquired from a decedent. "Step-up in basis" is common shorthand, but value can step down. See also Form 1041 for how estate records connect to inherited-property basis.
When property changes from personal to business or income-producing use, the depreciation basis may be limited to the lower of adjusted basis or fair market value at conversion. Sale-loss rules can use a different analysis.
Basis may carry over and be adjusted rather than reset to full fair market value. Boot, gain recognition, liabilities, and exchange costs can affect the result.
Basis also applies to ownership interests.
A partner has outside basis in the partnership interest, which can change for contributions, allocated income or loss, distributions, and the partner's share of certain liabilities. The partnership separately has inside basis in its assets. These are not interchangeable.
An S-corporation shareholder tracks stock basis and, separately, qualifying debt basis. Income and contributions can increase basis; losses and distributions can decrease it in a required order. The corporation does not generally maintain each shareholder's complete basis calculation.
Basis can limit whether an owner deducts a loss and whether a distribution is tax-free. Book equity, retained earnings, capital-account balances, and cash invested are useful records but do not automatically equal tax basis.
Depreciable basis begins with the applicable tax basis and may be reduced or allocated for land, credits, personal use, or other rules. Depreciation then reduces adjusted basis even when the taxpayer failed to claim depreciation that was allowable. This "allowed or allowable" concept can create a surprise gain on sale.
Business-use percentage also matters. A mixed-use vehicle or home cannot simply depreciate the entire purchase cost as business property.
California often begins with federal basis concepts, but federal and California adjusted basis can diverge. Common causes include different depreciation deductions, bonus-depreciation conformity, Section 179 limits, credits, prior state adjustments, and entity-level differences.
When basis differs, the federal and California gain, loss, depreciation, or distribution treatment may also differ. Taxpayers should maintain a separate California basis schedule rather than try to reconstruct the difference only when property is sold.
For inherited property, California generally follows applicable basis-at-death concepts, but the estate documents, valuation, ownership, community-property status, trust terms, and federal elections must be reviewed.
Basis records often need to be kept as long as the asset or interest is owned, plus the applicable limitations period after the final tax effect.
Heath Income Tax can reconstruct and maintain federal and California basis schedules, calculate gain or depreciation, and coordinate asset and owner-basis reporting with individual, business, trust, and estate returns.
Is tax basis the same as market value?
No. Market value estimates what property is worth; basis is a tax measurement. They can be very different.
Can basis be negative?
Asset basis generally cannot fall below zero. Partnership and entity rules can involve liabilities and gain recognition, but a taxpayer should not simply record a negative asset basis.
Does refinancing change basis?
Borrowing against property generally does not increase or decrease its basis by itself. How the proceeds are used may create separate tax consequences.
Who tracks shareholder or partner basis?
The owner is responsible for substantiating basis, using entity returns, K-1s, contribution and distribution records, debt information, and prior calculations.
Why does California basis differ?
Federal and California depreciation, expensing, credits, or conformity rules can produce cumulative differences.
The definitions and examples on this page are for informational purposes only and do not constitute tax advice. Tax laws change frequently and individual circumstances vary. Consult a qualified tax professional before making decisions based on this content.
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