Thank you, Andrew, and thank you all for joining our call this morning to discuss ARMOUR's fourth quarter 2021 results. I'm joined today by ARMOUR's co-CEOs, Scott Ulm and Jeff Zimmer; and Mark Gruber, our Chief Investment Officer.
By now, everyone has access to ARMOUR's earnings release, which can be found on ARMOUR's website, www.armourreit.com. This conference call may contain statements that are not recitations of historical fact, and therefore, constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All such forward-looking statements are intended to be subject to the safe harbor provisions provided by the Reform Act.
Actual outcomes and results could differ materially from the outcomes and results expressed or implied by the forward-looking statements due to the impact of many factors beyond the control of ARMOUR. Certain factors that could cause actual results to differ materially from those contained in the forward-looking statements are included in the Risk Factors section of ARMOUR's periodic reports filed with the Securities and Exchange Commission. Copies are available on the SEC's website at www.sec.gov.
All forward-looking statements included in this conference call are made only as of today's date and are subject to change without notice. We disclaim any obligation to update our forward-looking statements unless required by law.
Also, our discussion today may include references to certain non-GAAP measures. A reconciliation of these measures to the most comparable GAAP measure is included in our earnings release.
An online replay of this conference call will be available on ARMOUR's website shortly and will continue for 1 year.
Since we last spoke, the interest rate and mortgage markets have been marked by choppy waters. ARMOUR's quarter end book value was $10.33 per common share, down $0.76 from September 30, 2021. This quarter-over-quarter decrease reflects spread widening across our MBS portfolio, which is likely the result of the market ruminating on talk of inflation, Fed interest rate hikes and future reductions in agency mortgage purchases. We expect this tightening and taper market will be with us for a while, and we're optimistic that it will remain relatively orderly and avoid throwing another tantrum.
For an apples-to-apples comparison across the sector, book value was $9.76 per common share on January 31, 2022. As the close of business on February 15, we estimated ARMOUR's book value per common share to be approximately $9.17. While spread widening negatively impacts the current market value of our existing MBS portfolio, it also reflects increasing current asset yields and improving opportunities for new MBS investments.
At December 31, 2021, ARMOUR's portfolio consisted of $4.4 billion of agency securities and TBA positions, representing another $4.5 billion. We also had $200 million of U.S. treasury securities. Since then, ARMOUR has reduced its agency and TBA portfolio by $2.9 billion and increased its U.S. treasury position by $1.6 billion to be ready to take advantage of those improving opportunities.
ARMOUR's Q4 comprehensive loss was $37.8 million, which includes $20.8 million of GAAP net loss. Distributable earnings, which excludes gains or losses from security sales and early termination of derivatives as well as market value adjustments, but it does include TBA drop income, was $27.7 million or $0.27 per common share.
During the fourth quarter, ARMOUR issued 6,386,724 shares of common stock through the ATM programs, raising $67.5 million of capital after fees and expenses. As we've discussed on prior calls, increases in our common share base reduced per share administrative costs. For the full year, ARMOUR's common share count is up 44%, which reduces the administrative expense load by $0.17 per common share on an annualized pro forma basis.
ARMOUR Capital Management, the company's external manager, continues to waive a portion of its management fee. The waiver currently offsets $650,000 of operating expenses each month.
The company paid dividends of $0.10 per common share for each month in the fourth quarter for a total of $30.9 million. ARMOUR maintained that monthly dividend rate of $0.10 per share with the recently announced March 2022 common dividend. The Series C preferred stock dividends for Q1 2022 have also been declared at the contractual rate of 7% per annum.
Now I'll turn the call over to Co-Chief Executive Officer, Scott Ulm, to discuss ARMOUR's portfolio positioning and current strategy in further detail. Scott?