If someone claims you have infringed on their trademark, you need to examine several things.
Firstly, you’ll need to understand whether the complaining party actually had the trademark and whether they had legally protected it. Just because someone once designed a particular logo or wrote a specific word or phrase does not necessarily mean they hold the trademark to it. Maybe they just had it lying around on a sketch pad but had never so much as shown it to someone else, let alone registered it.
Then, you need to examine what alleged infringement occurred. There are two grounds for a claim that you could potentially pursue.
The other party’s use could confuse customers
Let’s say you make candies, and the party accusing you of infringement makes cars. They are unhappy you have produced a sweet with the same name as one of their vehicles. No one is going to walk into a candy store and think the item on display for a dollar is actually a car. They might, however, assume some association between the car manufacturer and the sweet of the same name. Have they sponsored it? Are they endorsing it? The car manufacturer may try to claim that selling a candy bar with the same name as their vehicle may confuse customers to a degree, which trademark protections are designed to safeguard against.
The other party’s use could dilute the original trademark
Let’s say the vehicle in question is a beefed-up machine for people who want to believe they are setting off on a true adventure each time they take the wheel. It comes in a limited range of colors the company has deemed appropriate for that rough and tough image. They are livid when they see your pink-wrapped candy bars bearing the same name. They claim it is diluting their trademark by softening the tough image they had built.
Whether or not a trademark infringement occurred is often up for debate. Seeking legal guidance to effectively argue your case will be crucial, whatever side of a dispute you are on.