Quick answer: Yes, always. Here's why.
Almost all modern automotive paint systems are designed to use clear coat. All major vehicle manufacturers use it, all body shops use it, and any reputable touch up company should too.
Clear coat protects your paint’s color. It has UV and chemical resistance as well as other protective qualities. But in addition to that, paints are actually engineered with clear coat in mind. So without clear coat, you may not get the correct, true color you want.
Without going into much detail, the clear coat is needed to achieve the proper finish and it will be the protection your paint needs to last for years. Do not skip this step —- always use clear coat.