Thanks to the good folks at The SEC Institute for this:
As you likely know, the SEC added a check box on the cover pages of Forms 10‑K and 10‑Q concerning the filing and posting of XBRL (interactive data) files. The wording in the check box is a bit ambiguous, so the staff issued this C&DI to clarify how to complete the check box:
Question: If a company is not yet required to submit Interactive Data Files with its Exchange Act reports, should it check the box on the cover pages of the reports relating to compliance with Interactive Data File submission requirements?
Answer: No. A company should not start checking the cover page box relating to Interactive Data File compliance until it is required to submit those files. For example, if a company is first required to include an Interactive Data File with its second quarter Form 10‑Q and, as permitted by the grace period rules, includes such file in a Form 10‑Q amendment 30 days after the date the report is due and filed, the company should not check the Interactive Data File box on the cover page of its initial Form 10‑Q. Rather, it should check the box once the first Interactive Data File is submitted — in this case, with the Form 10‑Q amendment. Companies that have been voluntarily submitting Interactive Data Files should not check the box until they are required to submit the files. [Apr. 30, 2009]
You can find this C&DI at: