Is there any adjectival form of "Audit"?

I just made the mistake of using "Auditory" in the context of auditing. For example:

"We need to include that information, for auditory purposes."

After I sent my e-mail, I was embarrassed to find out that "auditory" refers to hearing.

I'm not recommending the phrasing when I say 'auditorial' works in your example sentence:

We need to include that information, for auditorial purposes.

I'm sure there are better ways to put it, depending on context and intention. For example:

1. We need to audit that information.
2. That information must be included for the audit.
3. Etc.

From OED:

auditorial, adj.
...
2. Of or pertaining to auditors of accounts; connected with an audit.

In your example, the purposes are connected with an audit.