It wasn’t long after ChatGPT began generating realistic images that Anant Kale started seeing posts on social media that explained how it could be used to generate a pretty convincing fake receipt.

That was, he recognized, his problem.

As the chief executive of AppZen, a software used by finance teams to manage expenses, he had overseen the creation of fraud-detection tools that flagged A.I.-generated receipts. But this was different.

“We were like, oh, shoot, this is too easy,” he told DealBook.

AppZen immediately started developing a tool to detect fake receipts generated by chatbots. It’s not the only one: The expense management app Expensify added ways to detect A.I.-generated receipts in April, and SAP Concur’s automated expense-auditing tool, Verify, expanded a similar capability to all users this month.

This summer, when announcing new efforts to flag A.I.-generated receipts, Nicolas Ritz, who works on product development at the corporate travel software company Navan, summed up the dilemma:

“A.I.-generated receipts will only get better from here,” he wrote. “To combat fraudulent A.I., we need to use A.I.”

Expense fraud can be a slippery slope. Kale said it’s common for employees to generate their first fake receipt to account for a legitimate expense. Maybe they lost the receipt. But when they don’t get caught, they do it again. Occasionally, the fraud is egregious. AppZen once detected a batch of A.I.-generated receipts submitted by a company employee for hotels and airfare in Bangkok — a city that, upon further investigation, the employee had not visited.

The Association of Certified Fraud Examiners, which certifies about 5,000 new examiners each year, regularly asks members to submit the largest case of occupational fraud they’ve investigated in the last 18 months. In the most recent survey, about 13 percent of the cases involved employees who submitted inflated or invented expenses, which can lead to criminal charges. The median loss was $50,000.