Tax Lien certificates is a direction either to earn x amount of interest on the face value of the tax certificate plus the amount you invest on the deed application or take ownership on the property. Dealing with tax certificates involves time on researching for the good ones, time selling them and making a profit, time for the deed application process and time going to the public auction in the county to bid for it and perhaps own it. Tax certificates differ among the nation. For instance, in the state of Florida the interest is 18% and other states interest are less or higher. People invest on tax certificates because their earnings of interest are better than the banks can pay .