When doing business, be careful not to receive a bad check.
Tips
register
Taiwan colloquial. 芭乐 (guava) is widely available and dirt-cheap in Taiwan, so a 'guava check' is a check that's worthless when you try to cash it. Mainland speakers say 空头支票 (kōngtóu zhīpiào).
culture
By extension 芭乐 alone in Taiwanese slang can mean 'cheesy / generic / rip-off' (as in 芭乐歌 'a generic pop song') — same idea: cheap and overdone.