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 .
I. Use to join words that together are a single unit of meaning. This is the most common way to use a hyphen. When a group of words modifies a noun, link them together with hyphens. The test above applies to this usage.