In my area you don’t bid on the amount. You bid dwon on the rate. If you win, you pay the full tax due. When the owner pays the late taxes (the ones you have already paid) you get your money back plus the interest you bid. If they don’t pay, you get the property after 3 years. One caveat though - if you want the property you will need to keep paying the taxes for the following years until you get the property or the owner pays the back taxes.
I understand that in different parts of the country it works differently.
Just read this and find the reply interesting. Most tax lien sales are not online but rather in person. You can either bid down the interest rate or bid up the value. But in all cases where I have been to a sale they give several hours to pay and I would go to the bank and get certified funds.
I’m from a Tax Deed State, so my answer my not be completely relevant but you needed to have certified funds before the end of the bidding on the very next item or it was immediately rebid. One guy last week had a cashiers check for 5k. Well he bid 5k on a piece of land, and when he got up to make payment, they found out he didn’t have enough to cover the title transfer fee (an additional $57) so after the close of the next item. They immediately rebid his property.
So, look on the sale website. There will be a link to the Terms of the Sale. Read it carefully, it will tell you exactly how the transaction must go. Never forget these are run by the government. There is a whole section of laws that detail all of the minutia that you will have questions about.
Just so you know, the rules in Texas vary per county and in some counties they also vary. In Harris county you have to get in line to pay for your winning bid, no change is given. They continue the sale while you are on line paying and you can also bid for subsequent properties while on the line to pay. If you do not get on line to pay the Constable may just yell at you. I should know, I did not go in the line immediately and he was upset.