Perfection is a legal term to describe the final step in a process required to permanently secure a legal right. It has application in the law of real property, security of personal property, trade marks and patents. It used to be a key feature of American copyright law, but since recent reforms to bring international law on copyright closer together, it has a lesser importance.

If a legal right is not perfected, the person with the right may still have remedies available, but they may be subordinated to another person, or certain remedies may no longer be available to them.

In most cases, perfection is achieved when the legal interest is registered with a government department. This serves to give notice to any interested party of the existence of the legal right. In other cases, perfection may be achieved when a person with interest takes possession of personal property.

For example, in most jurisdiction, there exists a system to file a lien against real property for improvements made to the property. The process to perfect the lien so that it is enforceable against anyone with an interest in the property is generally to:

  1. Give notice to the property owner of the lien
  2. File the lien with the registry office
  3. Issue a claim in a court office based on the lien
  4. Obtain a court certificate showing that the claim has been issued; and
  5. File the certificate with the registry office

The lien is "perfected" when the last step is taken, even though the lien claimant may still have rights prior to taking the last step. However, if the steps are not taken in the right order, or there is a deficiency in any step of the process, or the steps are not completed in time, the lien can be vacated. In addition, if the last step is not taken, the lien claimant may not have a valid claim against the property if ownership changes hands for any reason. This does not mean the lien claimant may not have any remedies, but they would lose the right to ask that the property be sold to settle the lien.

The general rule with competing security interests is that it is the first party to perfect who gets priority, not the first party to start the path to perfection.