People tend to believe their spreadsheets are more accurate than they really are.
Caulkins, Morrison, & Weidemann (2006)
It is now widely accepted that errors in spreadsheets are both common and potentially dangerous.
Nixon & O'Hara (2010)
Even obvious, elementary errors in very simple, clearly documented spreadsheets are... difficult to find.
Galletta, et al (1993)
Spreadsheets are commonly used and commonly flawed.
Caulkins, Morrison & Weidemann (2008)
Spreadsheets are notoriously error-prone.
Cunha, et al (2011)
It is irrational to expect large error-free spreadsheets.
Panko (2013)
94% of the 88 spreadsheets audited in 7 studies have contained errors.
Panko (2008)
A lot of decisions are being made on the basis of some bad numbers.
Ross (1996)
The untested spreadsheet is as dangerous and untrustworthy as an untested program.
Price (2006)
Every study, without exception, has found error rates much higher than organizations would wish to tolerate.
Panko (1999)
Errors in spreadsheets are as ubiquitous as spreadsheets themselves.
Colbenz (2005)
Never assume a spreadsheet is right, even your own.
Raffensperger (2001)
Spreadsheets contain errors at an alarmingly high rate.
Abraham, et al (2005)
Programmers exhibit unwarranted confidence in the correctness of their spreadsheets.
Krishna, et al (2001)
Spreadsheets are more fault-prone than other software.
Kulesz & Ostberg (2013)
Spreadsheets are easy to use and very hard to check.
Chen & Chan (2000)
Errors in spreadsheets... result in incorrect decisions being made and significant losses incurred.
Beaman, et al (2005)
Most executives do not really check or verify the accuracy or validity of [their] spreadsheets...
Teo & Tan (1999)
...few incidents of spreadsheet errors are made public and these are usually not revealed by choice.
Kruck & Sheetz (2001)
The software that end users are creating... is riddled with errors.
Burnett & Myers (2014)
Spreadsheet errors... a great, often unrecognised, risk to corporate decision making & financial integrity.
Chadwick (2002)
Spreadsheet errors have resulted in huge financial losses.
Abraham & Erwig (2007)
Spreadsheets... pose a greater threat to your business than almost anything you can imagine.
Howard (2005)
60% of large companies feel 'Spreadsheet Hell' describes their reliance on spreadsheets.
Murphy (2007)
Spreadsheets are extraordinarily and unacceptably prone to error.
Dunn (2010)
Every study that has looked for errors has found them... in considerable abundance.
Panko & Halverson (1996)
Your spreadsheets may be disasters in the making.
Caulkins, Morrison, & Weidemann (2006)
Studies have shown that there is a high incidence of errors in spreadsheets.
Csernoch & Biro (2013)
Spreadsheets have a notoriously high number of faults.
Rust, et al (2006)
Most large spreadsheets have dozens or even hundreds of errors.
Panko & Ordway (2005)
Spreadsheets are alarmingly error-prone to write.
Paine (2001)
Spreadsheet errors are pervasive, stubborn, ubiquitous and complex.
Irons (2003)
The results given by spreadsheets are often just wrong.
Sajaniemi (1998)
The quality and reliability of spreadsheets is known to be poor.
Bishop & McDaid (2007)
Spreadsheet errors are still the rule rather than the exception.
Nixon & O'Hara (2010)
A significant proportion of spreadsheets have severe quality problems.
Ayalew (2007)
1% of all formulas in operational spreadsheets are in error.
Powell, Baker & Lawson (2009)
Untested spreadsheets are riddled with errors.
Miller (2005)
The issue is not whether there is an error but how many errors there are and how serious they are.
Panko (2007)
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Welcome to i spreadsheet verification

Do you trust your spreadsheets?

Spreadsheets are notoriously error-prone: research shows that 95% contain errors.

If your spreadsheets have not been verified, then you cannot trust that they produce reliable, accuracy, and robust results.

Spreadsheets need to be independently verified

We offer an independent verification service for Microsoft Excel spreadsheets, using sophisticated testing tools applied by spreadsheet experts.

Contact us to find out how we can help you to trust your spreadsheets.

Information about spreadsheet errors and testing

  • A description of how we test spreadsheets for errors.
  • Our blog about spreadsheet errors and testing.
  • Our spreadsheet risk assessment questionnaire.
  • A comprehensive bibliography of the spreadsheet error and testing literature.
  • Connexion, a collection of useful and interesting spreadsheet-related articles.
  • Our FAQ.
 

Recent tweets

Bibliography: "A risk and control-oriented study of the practices of spreadsheet application developers" http://t.co/SfzGSwrVPC #Excel
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Bibliography: "An evaluation of a structured spreadsheet development methodology" http://t.co/AYrDIjYLdF #Excel #spreadsheets
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Spreadsheet testing show case

  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">Example of a complex formula, using several <span class="showplus-captions-code">INDEX</span> functions.<br /> The formula also has inefficient repeated calculations, ie. <span class="showplus-captions-code">P$175/$J$182</span>.</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">Avoid substantial repetition, such as in this example. It would be better to divide this formula into two cells.<br /> eg. A1: <span class="showplus-captions-code">=INDEX(...)</span>; B1: <span class="showplus-captions-code">=IF(OR(ISNA(A1), A1=""), "", "Y")</span>.</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">Example of a boolean search technique. The search range can be in any sort order, so the formula may not behave as expected.</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">Example of a complex array formula - note the <span class="showplus-captions-code">{ }</span>. Contains nested boolean logic, repetition, an embedded constant (a poor practice known as "constant jamming") and nested <span class="showplus-captions-code">IF</span> functions.</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">Use of the <span class="showplus-captions-code">INDIRECT</span> function makes it difficult to verify a formula's correctness - especially when combined with other functions, as in this example.</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">What is the purpose of subtracting zero from <span class="showplus-captions-code">AG26</span> and <span class="showplus-captions-code">$R$4</span>? Perhaps those cells contain numbers formatted as text? This works in some functions but not others.</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">"Magic constants", also known as "constant jamming", are poor practice. What does the <span class="showplus-captions-code">1.5</span> mean?</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">Did you spot the potential error in the nested <span class="showplus-captions-code">IF</span>? ie. which clause did the developer intend to apply in the case that <span class="showplus-captions-code">V26=B12</span>? In this formula the nested <span class="showplus-captions-code">IF</span> is redundant anyway.</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">Uncommon functions, such as <span class="showplus-captions-code">MOD</span>, must be carefully tested.<br /> Did you know that the worksheet function <span class="showplus-captions-code">=MOD(-1,3)</span> and the VBA function <span class="showplus-captions-code">-1 Mod 3</span> give different results?</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">In this formula the inner nested <span class="showplus-captions-code">IF</span> statement is incomplete, so could produce a result of <span class="showplus-captions-code">FALSE</span> (rather than the intended result of zero).<br /> ie. the formula should end with <span class="showplus-captions-code">)),0),0)</span> rather an <span class="showplus-captions-code">))),0).</span></a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">A long, complex formula like this is very difficult to fully understand - even for the person who wrote it!<br /> How could you be confident that the formula is correct?</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">It is generally better to separate a formula like this into multiple formulae, so that the logic is clearer and the intermediate results are shown.</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">What does the "magic constant" <span class="showplus-captions-code">4</span> mean in this formula? Is the formula working with quarterly data? What if the formula was applied to monthly data?</a>
  • <a title="Click for more information" href="http://www.i-nth.com/index.php/resources/blog" style="color: #FFFFFF;">Why do the formulae in cells B4 and B5 give different results?<br /> Although B2 appears to contain a number it actually contains text, which the <span class="showplus-captions-code">+</span> and <span class="showplus-captions-code">SUM</span> functions treat differently.</a>
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