By Gillian Tan

It pays to double-check the numbers.

That’s the lesson Tibco Software Inc. and Goldman Sachs Group Inc. learned in the software company’s more than $4 billion sale to Vista Equity Partners, which is paying about $100 million less in the deal because of a spreadsheet mix-up.

— Andy McMillan for The Wall Street Journal

Goldman, Tibco’s adviser in the deal, used a spreadsheet that overstated the company’s share count to crunch the numbers in the deal, according to a regulatory filing.

“In its Sept. 27, 2014, presentation to the Board of Directors, Goldman Sachs, using the spreadsheet, used a share count that overstated [Tibco's] fully diluted common stock by the number of shares of restricted stock,” the filing says.

The error led to a miscalculation of Tibco’s equity value, a $100 million savings for Vista and a slightly lower payment to Tibco’s shareholders (roughly 61 cents for each outstanding share).

Tibco had agreed to pay Goldman $47.4 million for its services.

It’s not clear who created the spreadsheet. Representatives for Tibco and Goldman declined to comment. Vista couldn’t be reached for comment.

The error came to light after the deal was announced on Sept. 29, leading Goldman to revise Tibco’s implied equity value in the transaction to around $4.1 billion from $4.2 billion.

Goldman also revised the deal’s fairness opinion, saying the sale valued the company at 17.6 times the company’s adjusted earnings before interest, taxes, depreciation and amortization, or Ebitda, for the last 12 months, rather than the 18-times Ebitda it originally cited.

Despite the error, Tibco’s board decided not to change its recommendation to shareholders to vote in favor of the deal, the largest U.S. take-private deal in more than a year.

Four lawsuits challenging the deal have already been filed on behalf of shareholders, two in Delaware and two in California. Such lawsuits are standard fare when companies are bought and sold, but the error could give plaintiffs lawyers extra ammunition.