A business valuation is an argument. Arguments can be lost.
Most business valuations look credible on paper. The problem is that paper does not ask questions. Valuations are rarely challenged because they are arithmetically wrong. They are challenged because they are not defensible.
That distinction matters more than most people appreciate. A valuation is not just a number. It is an argument, and like any argument, it must hold up when someone with an opposing interest pushes back. In litigation, in due diligence, in a tax audit, or in front of a judge, the question is not only what did you conclude, but how did you get there, and can you justify every step under examination.
After working across transactions, disputes, and regulatory submissions in multiple jurisdictions, the same failure patterns appear with uncomfortable regularity. They are almost never about the maths. They are almost always about process, documentation, and independence.
The five most common reasons business valuations fail
1. The narrative and the numbers tell different stories
A business valuation is a narrative supported by numbers. The two must be consistent throughout. When an analyst describes a business as high-growth and operationally resilient in the narrative section, then applies a discount rate and growth assumption that implies the opposite, the document contradicts itself. That internal inconsistency is usually the first thing a scrutinising party identifies, and it undermines the credibility of the entire report, not just the section where the tension appears.
Defensible valuations are internally coherent. Risk factors identified in the qualitative assessment translate directly into specific, documented adjustments in the financial model. The narrative does not say one thing while the numbers quietly say another.
2. Discount rates and multiples without evidence behind them
Selecting an EBITDA multiple or capitalisation rate without clearly evidencing why that specific rate applies to this specific business, in this sector, at this point in time, is one of the most common and most avoidable sources of challenge. IRS Revenue Ruling 59-60 requires appraisers to reference comparable market data and document their reasoning explicitly. Citing industry standard as the sole basis for a significant assumption is not an argument. It is an open invitation to challenge. Comparable transaction data, sector-specific benchmarks, and identified risk premiums must all be documented and clearly connected to the conclusion.
3. Independence that is claimed but not demonstrated
Advisor bias, whether actual or reasonably perceived, is particularly damaging in dispute and regulatory contexts. If the valuer has a financial stake in the outcome or an ongoing relationship that creates pressure to reach a particular conclusion, the opinion starts from a compromised position. HMRC challenges frequently turn on the independence of the valuer and the quality of comparable evidence, as does IRS scrutiny in the United States. In legal proceedings, the declaration of independence in the bizval business valuation report is not a formality. It is part of the professional foundation of the opinion.
4. A documentation trail that cannot reconstruct the conclusion
A business valuation that cannot be fully reconstructed from its working papers is a business valuation that cannot be defended. If data sources are unnamed, adjustments are unexplained, and model inputs cannot be traced to documented evidence, the conclusion is effectively unverifiable. As DHJJ’s compliance guide on business valuation notes, under IRS guidelines a comprehensive report must detail the valuation methodology, key assumptions, and supporting financial and market data. Proper disclosure triggers the three-year statute of limitations on IRS challenges under Section 6501 of the Internal Revenue Code. Without it, the IRS can scrutinise the transfer indefinitely.
5. The methodology does not match the purpose
A value for tax purposes and a value for a transaction are not necessarily the same number, even for the same business on the same date. The applicable standard of value, the basis of value, and the relevant regulatory guidance all differ depending on the purpose. Using a transaction-focused methodology for a regulatory submission, or vice versa, creates an immediate technical vulnerability that an experienced opposing expert will identify and exploit. This is why bizval’s tax compliance valuations and bizval’s M&A valuations are purpose-built, not repurposed.
How scrutiny differs between the US and UK
IRS scrutiny in the United States: documentation and internal consistency
In the United States, IRS challenges to business valuations, particularly in estate and gift tax, charitable contribution, and business interest contexts, focus primarily on two things: whether the methodology is internally consistent throughout the report, and whether every assumption is documented to a standard that can withstand examination. Revenue Ruling 59-60 outlines eight factors appraisers must address. A report that inadequately covers any of them is exposed. Critically, the IRS does not need to prove the valuation is wrong. It only needs to demonstrate the process was insufficient. That is a meaningfully lower threshold.
HMRC and the Single Joint Expert standard in the United Kingdom
In the UK, HMRC disputes and court proceedings introduce additional complexity through the Single Joint Expert framework. Under the Civil Procedure Rules, the valuation expert’s overriding duty is to the court, not to the party that instructed them. A report that reads as advocacy for a client’s position will not survive this standard. According to the Expert Witness Journal, in nearly half of all cases where expert evidence is required in UK proceedings, a Single Joint Expert is appointed. HMRC challenges frequently turn on the quality and selection of comparable evidence, the independence of the valuer, and the transparency of assumptions underpinning the conclusion.
What a genuinely defensible business valuation looks like in practice
There are clear, practical markers that distinguish a business valuation report built to withstand challenge from one that is not:
- The narrative and the numbers are fully aligned: risk factors in the qualitative section translate directly into specific adjustments in the financial model
- Every significant assumption is sourced and evidenced: discount rates reference comparable data, multiples are benchmarked against identifiable transactions, and adjustments are explained rather than asserted
- The valuer’s independence is clearly stated and demonstrably true: particularly in dispute and tax contexts, this is part of the professional foundation of the opinion
- The purpose is stated up front and the methodology follows from it: the report is clear about what it is for and why the chosen approach is appropriate for those specific parameters
- Plain language is used throughout: a report that a non-specialist judge, mediator, or regulator cannot follow is a report that will not be persuasive, regardless of technical accuracy
If a business valuation is ever likely to be challenged, it should be built that way from day one. The cost of retrofitting defensibility after a challenge has been raised is almost always higher than doing it properly at the outset.
The question every advisor should ask before every instruction
For legal and tax professionals, M&A advisors, and accountants instructing valuations on behalf of clients, the most valuable shift in mindset is to ask, before the work begins: under what circumstances might this number be questioned, and does this report survive that test? That question alone changes the quality of the brief, the scope of the instruction, and ultimately the usefulness of the output. At bizval, it is the question we ask at the start of every engagement.
Frequently asked questions: business valuation failure and defensibility
Q: Why do business valuations get challenged by the IRS?
The IRS challenges business valuations most commonly because of internal inconsistencies in the report, inadequately documented assumptions, poor or thin comparable evidence, and a failure to address the eight factors required under Revenue Ruling 59-60. Importantly, the IRS does not need to prove the valuation is wrong. It only needs to demonstrate that the process was flawed. That is a lower threshold than most people realise, and it is why process and documentation matter as much as the number itself.
Q: What makes a business valuation defensible against HMRC scrutiny?
HMRC focuses primarily on three things: the independence of the valuer, the quality and selection of comparable evidence, and the transparency of the assumptions underpinning the conclusion. A bizval HMRC-aligned valuation is built to address all three proactively. Under the Single Joint Expert framework, which governs UK litigation proceedings, the valuer’s overriding duty is to the court, not the instructing party, which means the report must be objective and neutral throughout.
Q: What is the most common valuation mistake in M&A transactions?
In M&A contexts, the most common and costly valuation mistakes are: unsupported discount rates and multiples cited without comparable evidence; a quality of earnings analysis that fails to identify non-recurring or owner-related adjustments; and a valuation methodology that does not match the transaction structure. These are precisely the issues that bizval’s acquisition valuations and quality of earnings reports are designed to surface and resolve.
Q: Can an independent valuation protect against future challenges?
Yes, significantly. An independent business valuation prepared by a qualified specialist with no financial interest in the outcome, supported by documented methodology, evidenced assumptions, and alignment with applicable standards such as IRS Revenue Ruling 59-60 or IVS, provides the strongest available protection against challenge from tax authorities, courts, and counterparties. Under IRS guidelines, proper disclosure of a qualified appraisal also triggers the three-year statute of limitations on challenges under Section 6501 of the Internal Revenue Code. Without it, the scrutiny window is indefinite.
Q: What should an advisor ask before instructing a business valuation?
Before instructing any business valuation, the most important question an advisor can ask is: under what circumstances might this number be questioned, and does this report survive that test? That question determines the right level of independence required, the appropriate methodology for the specific purpose, the depth of documentation needed, and how the report should be structured and communicated. At bizval, it is the question we ask at the start of every single engagement.
CONCLUSION
The five failure patterns we have described are not rare edge cases. They appear across transactions, disputes, and regulatory submissions with uncomfortable regularity. And in every case, they were avoidable. The difference between a valuation that holds up and one that does not is almost never about the number. It is about the work that sits behind it.
At bizval, we build every independent business valuation to survive the room it will eventually be read in. Whether that room is a tax audit, a courtroom, a due diligence process, or a shareholder dispute, the standard is the same: documented, independent, purposeful, and defensible. Contact our team at bizvalglobal.com to discuss your specific situation.