Amazon told its corporate employees on Monday that they had to return to working in the company’s offices five days a week starting in January.

The new rule — up from a three-day-a-week mandate set in 2023 — appears to be the most stringent return-to-office decision among big tech companies and could be a harbinger of more to come.

That Amazon, which has always operated with tighter rules for its corporate work force than its peers, is leading the way back to the office is not a surprise. Amazon has over the years shunned plush corporate campuses and lavish employee perks common among tech companies, while giving managers attrition targets for how many people should leave their teams.

“If anything, the last 15 months we’ve been back in the office at least three days a week has strengthened our conviction about the benefits,” Andy Jassy, Amazon’s chief executive, wrote in a memo. Mr. Jassy said in-person collaboration allowed Amazon to move fast and retain its culture, which he said had become particularly hard to maintain as the company grew quickly during the pandemic. “We want to operate like the world’s largest startup,” he wrote. The change will affect more than 350,000 corporate employees. Amazon also has more than a million employees working in warehouses and operations.

An internal site for Amazon employees, viewed by The New York Times, said that attendance would be monitored by swipes of corporate badges, and that employees must return to the office even if there were not many members of their team in their location. It said the company was working to make conference rooms more available and was adding about 3,500 so-called phone booths in offices to accommodate the additional employees.

Amazon’s internal messaging channels lit up with discontent over the changes, according to screenshots of the messages. “The whole situation is just very depressing and de-motivating to say the least,” one message said. They also questioned how the changes fit with Amazon’s stated mission to become “Earth’s best employer.”

Since they essentially shut down their offices in the early days of the pandemic, tech companies have been inching toward getting employees back. Right now, other big tech companies like Microsoft, Google, Meta and Apple expect employees to work in the office two or three days a week.

Giving employees workplace flexibility allowed companies to save money on office space and to offer work flexibility as a perk. But executives are increasingly saying there have been trade offs that they no longer want to make.

As employers focus on productivity, they also note that outside the office people have returned entirely to prepandemic levels of activity.

“There is a sense the pendulum swung way too far in the opposite direction — this ‘the office is super optional,’” said Zach Dunn, co-founder of the workplace management platform Robin, which has helped companies put in place hybrid policies. “A lot of people are swinging back to this idea, ‘We were better off beforehand.’”

Nick Bloom, an economist at Stanford who studies work-from-home policies, noted that many companies had frequently done turnabouts on their return-to-office rules. In a February survey of more than 2,600 workers, nearly 40 percent said they had experienced two or more changes in company R.T.O. rules.

Offices across the country have reached over 50 percent of prepandemic occupancy, according to Kastle, the workplace security firm. Just over a quarter of paid workdays were done from home in August, according to research from Stanford.

At some companies, the specter of layoffs has motivated employees to spend more time in the office, wanting to strengthen in-person relationships. Amazon also said on Monday that it planned to increase the number of people a typical manager oversees by 15 percent by the end of March.

Mr. Jassy also said the company was making the change in order to flatten its organization, but employees questioned whether it could also open the door to layoffs.

Amazon left open the possibility that some managers could be laid off, according to an internal Frequently Asked Questions page with more details, viewed by The Times. It said each team would review their structure and, “it’s possible that organizations may identify roles that are no longer required.”

In the past, when Amazon has eliminated roles, it has laid off employees if they do not find or accept a new position at the company.