Why does costco hold an additional 100.00 out of my checking account and also the dollar amount of the gas purchase?.? Merry Christmas Costco

Some gas stations do that, usually with debit transactions. They usually return the money after a certain number of business days.

It might be your bank. I don't think mine does that.

Because they can. The banks allow it. I don't like it

Oh wow I didn't know that. I guess I'll to check myself! Sorry I couldn't help you