[bncinwv]

Not sure what kind of toilet, but one thing I have learned from this forum is to let the toilet ball valve slam shut. As a matter of fact, after "flushing" I do that two or three times. Press down and release all at once. After I learned this from the forum, I have never again had a problem with the toilet bowl holding water. On some toilets there is a band behind the toilet that can be tightened, almost like a hose clamp but obviously much larger. Try the slam method first though, you may be surprised.
Bingo