Find your form. To search, type in a keyword and/or choose a category. To search for archived forms from a previous tax year, choose a year in the drop down menu.
So don't worry so much about how to use  had had  as a unit of grammar, they will come together naturally when you want to express the verb ' to have ' in the past perfect. Let's consider a different verb for a moment like  to want .
What does it mean had have and have had? Well, they both mean the same thing but some people like to say 'had have' and some like to say 'have had'. It's just that they like to say it that way.