Question: I am looking to publish an audiobook on ACX, and I am 13 years old. **Is there any age restriction on publishing an audiobook on ACX?** For example, during registration, it asks me if I hold a US tax ID for the payments from ACX.

Answer: 
You must be 18 to publish on ACX.

But you can probably convince a parent/guardian to publish for you.

Amazon will also publish audiobooks, but you will still need a parent/guardian to publish for you since you are under 18.
There are pretty good reasons for most age restrictions.

In creating a book, an author cannot help but reveal a great deal about their personal worldview, their values, their beliefs and their dreams. At such a young age, most of that internal landscape is still evolving. The next five years of your life may include massive changes to any or all of those elements and the sum of those changes may leave you far from the person you currently are.

In publishing a book today, you may permanently associate your name, your pen-name and your talent, with enthusiasms and values which some future you might not share. If you are fortunate enough to succeed in earning a large following, that future you may resent being typecast by the words you've crafted today.

That you are already writing is spectacular! If you keep it up and keep refining your abilities, you will have a major advantage over your peers when you all finally reach legal publishing age. And more importantly, you will have five years of accumulated works, all meticulously reviewed, edited and finalized, ready all at once.

As a reader, compare the difference in experience between reading a trilogy in series over reading the first book of a trilogy and then waiting for years (or forever) for the second book. Use the next five years to create a complete trilogy (or several) so that you can give your readers that complete trilogy experience on day one.

Above all else, Keep Writing!