Often a trademark owner will send a cease and desist letter demanding that the infringing party stop using the mark. The infringement may not be on purpose and the infringing party may stop when notified that their conduct is in clear violation of another’s rights.
The infringing party may also ignore the demand or take the position that they are not infringing. At that point, you may consider a trademark infringement lawsuit. You should talk with an attorney if you believe a lawsuit might be the right choice for you.
Successful lawsuits have common characteristics and you should discuss with a lawyer whether any of these are present in your situation:

• The plaintiff is the owner of a valid mark, which is ordinarily presumed if they have a federal trademark registration.
• The other side is using the mark without authority in connection with the sale of goods or services.
• The other side is using the mark in a manner that is likely to cause confusion to reasonable consumers.

It is possible to amend an application, but the process and the associated fees generally depend on the timing of the changes. Changes before the trademark has been published in the Official Gazette can be made by logging into your US Trademark Legal account and requesting that a change be made. Additional fees and filing fees to the USPTO may apply.
Changes once the trademark has been published in the Official Gazette generally require a Post-Publication Amendment, which you may request through US Trademark Legal.
Depending on the scope of the amendment, an applicant may need to file a new application instead. Changing the mark entirely, for example, would require a new application. Broadening the scope of a description of goods/services or adding additional classes may require additional fees and would also likely require a new application. Clerical errors, on the other hand, are generally easy to fix and typically won’t affect the applicant’s place in line or require a new application.

Yes, like any other business asset, a trademark can be sold, licensed or assigned. Validity requirements generally still apply, so someone usually needs to continue to use the mark in commerce and it is helpful to register assignments with the USPTO. If you enter into such an agreement, we can help with a transfer of the trademark with the PTO. Sometimes, individuals register the mark before a company is officially set up. Then, once the company is formed, the mark needs to be transferred into the company.

According to the USPTO, trademark infringement is the unauthorized use of a trademark or service mark on or in connection with goods and/or services in a manner that is likely to cause confusion, deception, or mistake about the source of the goods and/or services.

According to the USPTO,“the key factors considered in most cases are the degree of similarity between the marks at issue and whether the parties' goods and/or services are sufficiently related that consumers are likely to assume (mistakenly) that they come from a common source. Other factors that courts typically consider include how and where the parties' goods or services are advertised, marketed, and sold; the purchasing conditions; the range of prospective purchasers of the goods or services; whether there is any evidence of actual confusion caused by the allegedly infringing mark; the defendant's intent in adopting its mark; and the strength of the plaintiff's mark.” These are all fact intensive inquiries.