One of the things that have to take place when purchasing a tax lien is making sure that you have everything in order that is required by the county.  If you are purchasing at an online tax lien auction, then you will already have these things in place. First you want to make sure that you have a bidder registration number.  Many of the counties have what is called a bidder registration form.  You can obtain this from the website or call the county and have them fax one to you.  This will give you a bidder number. If you do not fill out a bidder registration form, then you would need to send a letter along with your investment checks to the tax collector of that county or the collection department. Make sure that all of your contact information is on the letter.  Even the tax liens that are purchased over the counter or after the auction will be assigned a bidder number to them.   You will be known as that bidder when purchasing any tax liens, during an auction, or after the auction. One more thing that is necessary when you purchase any tax liens, is a W9 form.  This can be found on the irs.gov website under forms.  This is assurance for the county that you will be responsible for the taxes on the interest that you earn.  When you get a check from the county for the interest that you have earned then you will report the interest on your taxes.  For people from other countries that want to purchase in the United States, they will need to obtain an ITIN number or an EIN number to fill out the W9 form with.  This will allow them the opportunity to purchase tax liens from another country. Once these steps are in place then you will be secure in your purchases.  You may only receive a certificate by email regarding your recent purchase depending on what county you are working with, so if you would like a paper receipt then make sure that you request it from the county.   One more thing to remember is that when you send out checks to the county, make sure that you send separate checks for each parcel being purchased.  This will stop your money from being tied up in case one of the parcels that you want has already been purchased.