Error Trapping in Excel Through Flagging and Custom-Built Error Checks

Error Trapping in Excel Through Flagging and Custom-Built Error Checks

In the fast-paced world of investment banking, where complex financial models drive critical decisions, the importance of error trapping cannot be overstated. Even a single misplaced decimal or incorrect formula can lead to significant financial missteps. Thus, it is essential for finance professionals to master the art of identifying and managing errors in their Excel spreadsheets.

This blog post will delve into error trapping in Excel, focusing on flagging and custom error checks, using a practical dataset to illustrate the said techniques. Learn how to maintain accurate and reliable financial models and make informed decisions confidently.


Understanding Common Excel Errors in Finance

It is important to be aware of common errors, such as #VALUE!, #REF!, and #NAME?, that can occur when working with complex financial models in Excel.

  • The #VALUE! error typically arises when a formula expects a specific value, such as a number, but receives something else, like text. 
  • #REF! errors occur when a formula references a cell that no longer exists, often due to the deletion or modification of rows or columns. 
  • Lastly, #NAME? errors happen when Excel fails to recognize a function or named range used in a formula. 

Effective error trapping requires understanding common financial model errors and their occurrences. Even small mistakes can come with significant implications.

In 2012, JPMorgan Chase suffered a loss of more than $6 billion due to a series of errors in an Excel spreadsheet known as the ‘London Whale‘ incident. Another example is the Reinhart-Rogoff controversy, which resulted from a simple Excel error in a research paper on government debt and economic growth, leading to significant policy debates.

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Using the Dataset for Error Flagging

Before proceeding, you may download the Excel dataset template in the next section to try out the different error-flagging methods on your own.

A. Applying Conditional Formatting to Financial Data

One powerful tool for error trapping in Excel is conditional formatting. Using conditional formatting on financial data lets you quickly identify cells with missing or erroneous returns.

Step 1: To apply conditional formatting, select the cell range and go to ‘Conditional Formatting’ in the ‘Home’ tab.

Step 2: In the dropdown menu, choose ‘Highlight Cells Rules’ and ‘Equal To’

Step 3: In the dialog box, enter the value representing an error in your dataset, such as ‘0 for missing returns.

Step 4: Choose a formatting style that will make the cells stand out, like red fill with white text. 

The above visual cue will help you identify and address errors efficiently.

B. Data Validation for Investment Data

Another effective method for preventing errors in your financial models is to use data validation. This feature allows you to set constraints on cells to ensure valid data for calculations. 

Step 1: Select the cells with investment data, click ‘Data’, and click ‘Data Validation’ to apply validation.

Step 2: In the dialog box, choose the appropriate criteria for your data, such as ‘Whole number’ for investment amounts or ‘Decimal’ for returns.

Step 3: You can also set minimum and maximum values to prevent entries outside a reasonable range.

By implementing data validation, you can minimize the risk of erroneous data entries that could compromise the accuracy of your financial model.

Download Excel Template

Download Template

Download Template

Error Trapping in Excel

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Building Custom Error Checks for Finance

A. Error Detection with Excel Formulas

Excel offers a range of formulas for detecting and managing errors in financial data. Two handy functions are ISERROR and IFERROR. 

ISERROR returns TRUE if a cell has an error value and FALSE otherwise. 

Use an IF statement for custom error messages or alternative calculations when an error is detected.

For example, the formula =IF(ISERROR(A1), “Error in cell A1”, A1) will return the value in cell A1 if it is not an error, or the message ‘Error in cell A’ if it is.

The IFERROR function simplifies the above process by allowing you to specify a value to return if the first argument results in an error. Using the IFERROR function, if C5 is zero, ‘Division by zero’ will be returned instead of an error message.

=IFERROR(B5/C5, “Division by zero”)

By incorporating these formulas into your financial model, you can effectively trap and handle errors, maintaining the accuracy of your calculations.

B. Custom Error Check Columns in Investment Tracking

Maintaining consistent and accurate data when tracking investments and their returns is crucial. You can achieve this by creating custom error check columns that verify the data’s integrity.

For example, you can make a column that calculates the total investment amount by summing the individual investment entries and then comparing this total to a manually entered expected total using an IF statement. 

The formula =IF(SUM(B2:B6)=B7, “Totals match”, “Error in totals”) will return ‘Totals match’ if the sum of the investment entries in B2 – B6 matches the expected total in cell B7, or ‘Error in totals’ if there is a discrepancy.

Advanced Error Trapping Techniques for Finance Professionals

A. Leveraging VBA for Automated Error Handling

Although built-in Excel formulas provide a solid foundation for error trapping, more complex financial models may require the power and flexibility of VBA (Visual Basic for Applications) to automate error-handling processes. VBA enables you to create custom scripts to detect particular conditions, display error messages, and rectify mistakes. 

For example, a simple VBA script can loop through a range of cells, checking each value against a set of criteria and flagging any cells that fail to meet the said criteria. It can significantly reduce time and effort compared to manually checking cells, especially for large datasets. 

Additionally, custom error-handling routines can be created using VBA to manage specific errors in financial models, providing a more sophisticated level of error management.

B. Employing Array Formulas for Complex Financial Analysis

Array formulas are another powerful tool in the Excel arsenal that can help minimize errors in complex financial analyses. Unlike regular formulas that calculate individual cells, array formulas operate on multiple cells as a single entity. It allows for more complex, error-resistant calculations across entire investment portfolios. 

To calculate a portfolio’s weighted average return, you can use an array formula that multiplies each investment’s return by its weight, sums the results, and divides by the total weight. 

Array formulas reduce the risk of errors when linking multiple formulas across different cells and ranges.

Best Practices for Error Management in Financial Modeling

1. Establishing Routine Audits

Implementing error-trapping techniques is essential to maintaining the accuracy of your financial models. Still, it is equally important to establish a routine auditing process to ensure the techniques are applied consistently and effectively. Regular audits should involve:

  • Systematically reviewing your Excel spreadsheets
  • Checking for common errors
  • Verifying the accuracy of formulas and calculations
  • Ensuring that error-trapping measures function as intended

Depending on your organization’s size and complexity, a dedicated team member or an external auditor can oversee the above process. Regular audits in financial modeling proactively catch errors before they impact decisions.

2. Excel Training for Finance Professionals

To ensure financial model accuracy, provide ongoing training for your finance team to master Excel’s error trapping. Use online courses, workshops, and certifications to update your team on Excel techniques and best practices. Excel training for finance professionals ensures accurate financial models for informed decision-making.


In the dynamic and exacting world of investment banking, managing and preventing errors in Excel is vital. Possessing effective error-trapping skills can be a competitive advantage in financial modeling success. You can use Excel custom checks and advanced techniques like VBA and array formulas to improve the accuracy of your financial analysis. Regular audits and Excel training cultivate precision and excellence in finance teams.

At Macabacus, we understand the critical nature of such challenges. Our tools simplify financial documentation, increase productivity, and ensure consistency across different Microsoft Office applications. Macabacus provides you with the right tools to meet the high standards demanded by your industry, whether you are refining financial models or preparing complex presentations. Embrace Macabacus and take a significant step towards achieving excellence.

Create Financial Models 10x Faster with Macabacus

Gain access to 100+ shortcuts, formula auditing visualizations, easy Excel-to-PowerPoint linking and productivity tools to help you accelerate financial modeling and presentations.

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