UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q/A

Amendment No. 1

☒   Quarterly report pursuant to section 13 or 15(d) of the Securities Exchange Act of 1934

For the quarter ended September 30, 2017

or

☐   Transition report pursuant to section 13 or 15(d) of the Securities Exchange Act of 1934

For the transition period from ___________ to ____________

Commission File Number: 000-02040

Registrant's telephone number, including area code: (720) 407-7043

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Company was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.

YES ☒               NO ☐

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to rule 405 of Regulations S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).

YES ☒               NO ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See definitions of “large accelerated filer,” “accelerated filer”, “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).

YES ☐               NO ☒

Indicate the number of shares outstanding of each of the issuer's classes of common stock, as of the latest practicable date.

At November 10, 2017, there were 6,059,640 issued and outstanding shares of the Company’s common stock, $0.01 par value.

EXPLANATORY NOTE

Carbon Natural Gas Company (the “Company”) is filing this Amendment No. 1 on Form 10-Q/A (this “Amendment”) to re-file Exhibits 2.1 and 2.2 (the “Exhibits”) that were filed with the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2017, as originally filed with the Securities and Exchange Commission (the “SEC”) on November 14, 2017 (the “Original Form 10-Q”). This Amendment is being filed solely to re-file revised redacted versions of the Exhibits to reflect changes to the Company’s confidential treatment request with respect to certain portions of the Exhibits, and in connection therewith, to amend and restate Part II, Item 6 of the Original Form 10-Q. Nothing in the Original Form 10-Q is being amended other than as described above.

As required by Rule 12b-15 under the Securities Exchange Act of 1934, as amended, new Section 302 certifications are also filed as exhibits to this Amendment.

This Amendment should be read in conjunction with the Original Form 10-Q and the Company’s other filings with the SEC. Except as stated herein, this Amendment does not reflect events that occurred after the filing of the Original Form 10-Q and no attempt has been made in this Amendment to modify or update other disclosures as presented in the Original Form 10-Q.

PART II. OTHER INFORMATION

ITEM 6. Exhibits

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.