Under certain market conditions, it may be uneconomical for us to roll our TBA contracts into future months and we may need to take or make physical delivery of the underlying securities. If we were required to take physical delivery to settle a long TBA contract, we would have to fund our total purchase commitment with cash or other financing sources and our liquidity position could be negatively impacted. As of June 30, 2018, we had a net long TBA position with a total market value of $20.0 billion and a net carrying value of $105 million recognized in derivative assets/(liabilities), at fair value, on our Consolidated Balance Sheets in this Form 10-Q.
Our TBA dollar roll contracts are also subject to margin requirements governed by the Mortgage-Backed Securities Division ("MBSD") of the FICC and by our prime brokerage agreements, which may establish margin levels in excess of the MBSD. Such provisions require that we establish an initial margin based on the notional value of the TBA contract, which is subject to increase if the estimated fair value of our TBA contract or the estimated fair value of our pledged collateral declines. The MBSD has the sole discretion to determine the value of our TBA contracts and of the pledged collateral securing such contracts. In the event of a margin call, we must generally provide additional collateral on the same business day.
Settlement of our TBA obligations by taking delivery of the underlying securities as well as satisfying margin requirements could negatively impact our liquidity position. However, since we do not use TBA dollar roll transactions as our primary source of financing, we believe that we will have adequate sources of liquidity to meet such obligations.
Bethesda Securities Regulatory Capital Requirements
BES is subject to regulations of the securities business that include but are not limited to trade practices, capital structure, recordkeeping and conduct of directors, officers and employees. As a self-clearing registered broker-dealer, BES is required to maintain minimum net regulatory capital as defined by SEC Rule 15c3-1 (the "Rule"). As of June 30, 2018, the minimum net capital required was $0.3 million and BES had excess net capital of $321.1 million. Regulatory capital in excess of the minimum required by the Rule is held to meet levels required by clearing organizations, the clearing bank and other repo counterparties.
Asset Sales and TBA Eligible Securities
We maintain a portfolio of highly liquid mortgage-backed securities. We may sell our Agency securities through the TBA market by delivering them into TBA contracts, subject to "good delivery" provisions promulgated by the Securities Industry and Financial Markets Association ("SIFMA"). We may alternatively sell Agency securities that have more unique attributes on a specified basis when such securities trade at a premium over generic TBA securities or if the securities are not otherwise eligible for TBA delivery. Since the TBA market is the second most liquid market (after the U.S. Treasury market), maintaining a significant level of Agency securities eligible for TBA delivery enhances our liquidity profile and provides price support for our TBA eligible securities at or above generic TBA prices. As of June 30, 2018, approximately 90% of our fixed rate Agency RMBS portfolio was eligible for TBA delivery.
To the extent we raise additional equity capital we may use cash proceeds from such transactions to purchase additional investment securities, to make scheduled payments of principal and interest on our funding liabilities and/or for other general corporate purposes. There can be no assurance, however, that we will be able to raise additional equity capital at any particular time or on any particular terms. Furthermore, when the trading price of our common stock is significantly less than our estimate of our current tangible net book value per common share, among other conditions, we may repurchase shares of our common stock, subject to the provisions of a stock repurchase program in effect at such time.
OFF-BALANCE SHEET ARRANGEMENTS
As of June 30, 2018, we did not maintain relationships with unconsolidated entities or financial partnerships, such as entities often referred to as structured finance, or special purpose or variable interest entities, established to facilitate off-balance sheet arrangements or other contractually narrow or limited purposes. Additionally, as of June 30, 2018, we had not guaranteed obligations of unconsolidated entities or entered into a commitment or intent to provide funding to such entities.
This document contains forward looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These forward looking statements are based on estimates, projections, beliefs and assumptions of our management as of the date of this Quarterly Report on Form 10-Q and involve risks and uncertainties in predicting future results and conditions. Our actual performance could differ materially from those projected or anticipated in any forward looking statements due to a variety of factors, including, without limitation, changes in interest rates, the yield curve or prepayment rates; the availability and terms of financing; changes in the market value of our assets; the effectiveness of our risk mitigation strategies; conditions in the