Short answer
A reconciliation is the page in a cost segregation study where every allocated dollar is added back up and compared with the actual basis of the property. If the total ties, the study has at least accounted for everything once. If it does not, the difference is a finding, and the kind of difference tells you what went wrong: a missing document, a double-counted component, an unallocated indirect cost, a land split that moved, or a unit cost from the wrong year. The IRS's Audit Techniques Guide lists reconciliation of allocated costs to actual costs among the elements of a quality study and describes examiners checking that the study ties to the taxpayer's records. This article explains what a reconciliation contains, how to read a difference, and how practitioners and reviewers use it to find errors before anyone else does. It is general education for people learning the work, not tax advice.
What a reconciliation contains
| Line | Source | Note |
|---|---|---|
| Capitalized basis | Closing statement plus settlement costs that enter basis; or construction cost records plus owner soft costs | The control total; everything below must sum to it |
| Less land | The land allocation with its evidence | Not depreciable |
| Depreciable basis | Arithmetic | The pool the study classifies |
| 5-year property | Asset list | Each asset marked actual or estimated |
| 7-year property | Asset list | Same |
| 15-year land improvements | Asset list | Same |
| Indirect costs allocated | Indirect cost schedule | Method stated |
| Building (27.5- or 39-year) | Residual or costed | Stated as residual when it is one |
| Total allocated | Arithmetic | Must equal depreciable basis |
| Difference | Arithmetic | Zero, or explained |
The asset list behind the reconciliation ties to the fixed-asset ledger the tax adviser keeps, which is the other tie the guide expects.
Reading a difference
A reconciliation that does not tie is not a failure; it is information. Each pattern points somewhere.
- Allocated total exceeds basis. Components have been priced at more than the property cost. Usual causes: unit costs from today rather than the acquisition year; replacement cost used for aged components; a component counted in two trades; indirect costs added to components that already included them. The fix is in the take-offs and unit costs, not in shrinking the building line to force a tie.
- Allocated total falls short of basis. Something is missing. Usual causes: a document not received, an owner-paid soft cost not captured, site work outside the contractor's scope, personal property bought separately. The residual method hides this error by absorbing the shortfall into the building; a reconciliation that shows the building as a residual should also show what the residual implies per square foot and whether that is plausible.
- Basis itself is wrong. The closing statement was read without settlement costs, or with financing costs that do not belong, or the land split used a later appraisal. Publication 551 sets the rule: cost plus certain settlement costs, allocated by fair market value at purchase. Fix the top line before touching anything below it.
- Indirect costs unallocated. Architect's fees, permits and general conditions sit in a lump outside the components. Section 263A requires a properly allocable share of indirect costs to be capitalized; the study allocates them across components by a stated method, and the reconciliation shows the allocation.
- De minimis items treated inconsistently. Items the taxpayer expensed under a de minimis safe harbor election are not in basis and must not be in the asset list; items capitalized must be. The adviser's election determines which, and the study follows it.
- Rounding and conversion. Small differences from rounding unit costs or converting quantities are shown as such, not hidden.
Why reviewers read the reconciliation first
A reviewer with one hour reads the reconciliation, the land split and the asset list, in that order. The reconciliation tells them whether the study is arithmetically closed; the land split tells them whether the pool was established; the asset list tells them whether the classifications have reasons. A study that ties but rests on an unsupported land line is not sound; a study whose components are all reasoned but whose total is short of basis by a large amount has missed something. The reconciliation is the map of where to look.
Examiners use it the same way. The guide tells them to request the complete study and workpapers and describes checking that the study's costs reconcile to the taxpayer's records. A practitioner who builds the reconciliation as part of the work, rather than as a page added at the end, has already done the examiner's first test.
Building the reconciliation as you work
- Start from the control total. Establish capitalized basis and the land split before costing anything. Every later number has a ceiling.
- Mark every asset actual or estimated. The reconciliation should show the share of the total that rests on records and the share that rests on estimates. A study that is 90 percent estimated on a new building with full records is asking for trouble.
- Keep the indirect costs separate until the end. Allocate them once, by a stated method, and show it.
- Tie to the ledger. The asset list is what the adviser enters; if the ledger and the study disagree, one of them is wrong.
- Explain, do not absorb. A difference that is understood and stated is a limitation; a difference that has been pushed into the building line is an error waiting to be found.
- Reconcile again after every change. A revised unit cost, a component moved between classes or a corrected land value changes the total. The final report carries the final reconciliation.
A short case
A practitioner prices the components of a purchased apartment building from take-offs and published unit costs. The allocated components plus indirect costs come to more than the depreciable basis, leaving a negative building residual. Nothing about the classifications is wrong, but the reconciliation says the study cannot be right. The cause is found in the unit costs: they were current-year costs applied to a building bought several years earlier at lower prices. Repricing to the acquisition year brings the components down, the building residual becomes positive and plausible, and the report notes the pricing basis. Without the reconciliation the study would have gone out overstating every component.
Reconciling an existing building
On a look-back study the control total is the original capitalized basis as it appears on the depreciation schedule, not today's value and not the price plus later improvements. The reconciliation therefore has two ties instead of one: the study's asset list to the original basis, and the depreciation actually claimed to date to the schedule, because the section 481(a) adjustment is computed from both. Improvements made since acquisition are reconciled separately, each to its own cost, with its own placed-in-service date.
Common reconciliation errors
- Reconciling to the contractor's total instead of the capitalized basis.
- Leaving land in the pool and reconciling to the full purchase price.
- Reporting a building residual without checking it for plausibility.
- Absorbing an unexplained difference into the largest line.
- Failing to update the reconciliation after revisions.
- Not marking which costs are actual and which are estimated.
What people ask on Reddit and other forums
The searches that lead people to these threads are usually phrased "cost segregation reconciliation", "cost segregation workpapers", "reconcile to basis".
Reviewers on r/Accounting and owners in "cost segregation reddit" threads both ask, in different words, how to tell a real study from a spreadsheet. From the sources below:
"What is the first thing to check in a study?" The reconciliation: does the sum of land and every classified component equal the capitalized basis, and is any difference explained?
"The study ties to the penny. Is it good?" It is arithmetically closed. The land split, the classifications and the unit costs are checked separately.
"The building is shown as a residual. Is that a problem?" Not by itself when the building cannot be costed directly, provided the report says so and the residual is plausible. A residual that absorbs an unexplained gap is the problem.
"Who is responsible for reconciling?" The practitioner prepares it; the adviser checks that the study ties to the ledger and the return.
Questions people also ask
What does it mean if a study reconciles to the penny?
That the arithmetic is closed. It does not prove the land split, the classifications or the unit costs are right; it proves everything was counted once. Reviewers check those separately.
Should the building always be a residual?
Only when the building's components cannot be costed directly. With full construction records the building can be costed like any other component, and the reconciliation then has no residual to hide anything in.
How large a difference is acceptable?
None that is unexplained. Small differences from rounding are shown and described; anything else is investigated.
Who owns the reconciliation, the practitioner or the adviser?
The practitioner prepares it as part of the study. The adviser checks that the study's total and asset list tie to the ledger and the return.
Does the IRS require a reconciliation?
The guide lists it among the elements of a quality study and describes examiners checking that the study ties to the records. A study without one is missing what the examiner will ask for first.
Sources
- https://www.irs.gov/pub/irs-pdf/p5653.pdf — IRS Publication 5653, Cost Segregation Audit Techniques Guide (Rev. 2-2025): Chapter 4, principal elements; Chapter 5, review and examination.
- https://www.irs.gov/publications/p551 — IRS Publication 551 (Rev. December 2024), Basis of Assets.
- https://www.law.cornell.edu/uscode/text/26/263A — 26 U.S.C. §263A.
- https://www.law.cornell.edu/cfr/text/26/1.263%28a%29-1 — 26 C.F.R. §1.263(a)-1(f), de minimis safe harbor election.