What causes toilet tank to leak on top of toilet when flushed?

A toilet tank may leak on top when flushed due to several reasons, primarily a faulty or improperly sealed tank-to-bowl gasket. This gasket can wear out over time, allowing water to seep out during the flushing process. Additionally, a cracked tank or loose bolts securing the tank to the bowl can also contribute to leaks. Regular inspection and maintenance can help identify and resolve these issues promptly.