Would getting your 9 month old cat fixed stop it from peeing all over house?

No, neutering alone will generally not stop a 9 month old cat from peeing all over the house. This is because inappropriate urination is often caused by other underlying medical or behavioural issues, such as stress, anxiety, territorial marking, UTI or bladder stones. Once these issues have been identified and addressed, then you can consider your options to stop your cat from peeing all over the house. Neutering is primarily useful for eliminating unwanted behaviours related to sexual and reproductive urges.