Depends on the exact "IQ" test but many do not have an upper bound. The thing to understand about IQ tests is that they were designed and are primarily used as a diagnosis tool by psychologists to identify learning deficiencies. There really isn't much evidence that having a 180 vs a 140 IQ means a whole lot of anything beyond one's ability to take that specific test. If anything, having an extremely high score outside of the normal range may indicate neuro-divergence and likely savant syndrome. Some people are savants in specific ways - working memory, pattern recognition, language skills, etc. IQ tests certainly test several different categories of intelligence, but also certainly leaves out a few other known forms of intelligence.