Tai Sui (太岁) is the annual ruling energy of the year — specifically, the Earthly Branch of the year. "Offending Tai Sui" (犯太岁) means your personal chart's Branches clash, harm, or punish the year's Branch.
It happens when your chart contains the zodiac animal that directly clashes the current year's animal. For example, in a Horse year, people born in Rat years face a direct clash. There are also milder forms — harming, punishing.
It doesn't happen to everyone every year. But over a 12-year cycle, almost everyone experiences it at least once, because everyone has multiple Branches in their chart.
Traditionally, it's a year to be more mindful — not a curse, but a signal to drive carefully, communicate clearly, and avoid unnecessary conflicts.