My 7 year old cat, Kiki, for years has urinated on any piece of fabric that is left on the floor, from clothes, socks, and even our Christmas tree skirts. I have changed the type of litter I use as well as the litter box and clean it out daily. She is a little overweight, and I've been trying to control this problem with weight control food. There haven't been any significant changes in our house recently that could cause any stress.
After some research, I thought that it may be a UTI. However, this has continued for years, and from what i have read it would have been fatal by now. I have 2 other cats that she gets along with well and she gets all of her routine shots and deworming. I mainly keep her inside, with a couple of hours a day of outside privileges.
I'm in desperate need of help, because I will be forced to find her a new home if I cannot alleviate this problem.
You are not alone in your problem of having a cat urinating outside the box. The first step, however, is to officially rule out any medical underlying cause for her behavior. She could, in fact, have a UTI, even though the behavior has gone on for years, and should have a urinalysis done by a veterinarian as soon as possible. In addition, metabolic diseases, parasites, and many other things can cause inappropriate urination. For this reason, a thorough vet exam is recommended before assuming the issue is behavioral.
For more information on cat elimination problems and suggestions for helping your kitty, please see this page.