Corporate insiders have been actively buying and selling their own stock in May, with one recent weeklong stretch showing higher ups at five different companies spent at least $1 million, according to VerityData. Professional investors often watch insider transactions for potential clues about what the management team thinks about a company. While buys and sells can be made for personal reasons or on preset schedules, the idea is that some insiders are more likely to buy a stock they think is undervalued or to sell a stock they view as undervalued. The transactions listed below, disclosed in securities filings and compiled by VerityData, happened between May 9 and May 15. The biggest insider stock purchase came from Shift4 Payments CEO Jared Isaacman. VerityData labeled it as a “High IQ buy” as Isaacman saw his stock rise over the following 12 months after two previous purchases he made. However, it should be noted that Shift4 Chief Financial Officer Nancy Disman sold 10,000 shares the same week, according to securities filings. A similar situation happened at Akamai Technologies , where CEO Tom Leighton bought about $2 million worth of stock last Tuesday. This was also labeled by VerityData as a “High IQ buy.” However, Executive Vice President Anthony Williams sold a smaller amount of stock the same week, which could dampen the excitement about Leighton’s move. A more unified front comes at pharmaceutical company Biohaven , where director John Childs bought a little more than $1 million of stock on May 13. Childs, along with director Gregory Bailey and CEO Vlad Coric, have made multiple stock purchases over the past year, according to VerityData. Despite the insider buying, shares of Biohaven are still down more than 6% year to date. Insider sales The dollar figures attached to major insider sales during the same time period were even larger than the buys. Arista Networks CEO Jayshree Ullal had the biggest individual sale, at more than $13 million. Those sales come as Arista’s stock is trading near all-time highs. Meanwhile, Crowdstrike CFO Burt Podbere sold about $8 million of stock, with chief security officer Shawn Henry also selling shares. The CEOs of Squarespace and T-Mobile each sold more than $6.5 million worth of stock. It is worth noting that Squarespace CEO Anthony Casalena’s sales came before the May 13 announcement that the company had agreed to a buyout deal with private equity firm Permira. All of those above sales were made as part of a 10b5-1 trading plan, according to the securities filings and VerityData. One CEO that sold outside of that type of predetermined plan was Sweetgreen CEO Jonathan Neman, selling 200,000 shares for more than $6 million. Two other C-suite executives at Sweetgreen also made multimillion-dollar sales that week, according to VerityData. Sweetgreen shares have nearly tripled since the start of the year. — CNBC’s Nick Wells contributed reporting.