currencies other than the U.S. dollar are limited to 100% of the maximum revolving credit amount, as defined. The initial maturity date of the Supplemental Facility is January 31, 2026 and can be extended for an additional year to January 31, 2027 at our sole option, subject to satisfying certain customary conditions precedent.
Borrowings under the Supplemental Facility bear interest, at the Company’s election, at either (i) (x) for Term Benchmark Loans, the Adjusted Term SOFR Rate, the applicable Local Rate, the Adjusted EURIBOR Rate, or the Adjusted TIBOR Rate, (y) for RFR Loans, if denominated in Sterling, SONIA plus a benchmark adjustment and if denominated in Dollars, Daily Simple SOFR plus a benchmark adjustment, or (z) for Daily SOFR Loans, the Adjusted Floating Overnight Daily SOFR Rate, in each case of clauses (x) through (z) above, plus a margin determined by our corporate credit rating of between 0.650% and 1.400% or (ii) for loans denominated in U.S. Dollars only, the base rate (which rate is equal to the greatest of the prime rate, the federal funds effective rate plus 0.500% or Adjusted Term SOFR Rate for one month plus 1.000%) (the “Base Rate”), plus a margin determined by our corporate credit rating of between 0.000% and 0.400%. The Supplemental Facility includes a facility fee determined by our corporate credit rating of between 0.100% and 0.300% on the aggregate revolving commitments under the Supplemental Facility. Based upon our current credit ratings, the interest rate on the Supplemental Facility is SOFR plus 72.5 basis points, plus a spread adjustment to account for the transition from LIBOR to SOFR.
The Operating Partnership also has available a Commercial Paper program of $2.0 billion, or the non-U.S. dollar equivalent thereof. The Operating Partnership may issue unsecured commercial paper notes, denominated in U.S. dollars, Euro and other currencies. Notes issued in non-U.S. currencies may be issued by one or more subsidiaries of the Operating Partnership and are guaranteed by the Operating Partnership. Notes are sold under customary terms in the U.S. and Euro commercial paper note markets and rank (either by themselves or as a result of the guarantee described above) pari passu with the Operating Partnership’s other unsecured senior indebtedness. The Commercial Paper program is supported by the Credit Facilities and, if necessary or appropriate, we may make one or more draws under either of the Credit Facilities to pay amounts outstanding from time to time on the Commercial Paper program. On September 30, 2023, we had no outstanding balance under the Commercial Paper program. Borrowings reduce amounts otherwise available under the Credit Facilities.
On June 1, 2023, the Operating Partnership completed the redemption, at par, of its $600 million 2.75% notes at maturity.
On April 28, 2023 the Operating Partnership completed a borrowing of $180.0 million under the Credit Facility and subsequently unencumbered two properties.
On March 8, 2023, the Operating Partnership completed the issuance of the following senior unsecured notes: $650 million with a fixed interest rate 5.50%, and $650 million with a fixed interest rate of 5.85%, with maturity dates of March 8, 2033 and March 8, 2053, respectively. The Operating Partnership used a portion of the net proceeds of the offering to fund the optional redemption of its $500 million floating rate notes due January 2024 on March 13, 2023.
On January 10, 2023, the Operating Partnership completed interest rate swap agreements with a combined notional value at €750.0 million to swap the interest rate of the Euro denominated borrowings outstanding under the Supplemental Facility to an all-in fixed rate of 3.81%. These interest rate swaps mature on January 17, 2024.
On November 16, 2022, the Operating Partnership drew €750.0 million ($779.0 million U.S. dollar equivalent as of the issuance date) under the Supplemental facility and used the proceeds on November 17, 2022, to repay €750.0 million ($777.1 million U.S. dollar equivalent as of the payoff date) of senior unsecured notes at maturity.
On January 11, 2022, the Operating Partnership completed the issuance of the following senior unsecured notes: $500 million with a floating interest rate of SOFR plus 43 basis points, and $700 million with a fixed interest rate of 2.650%, with maturity dates of January 11, 2024 and February 1, 2032, respectively. The proceeds were used to repay $1.05 billion outstanding under the Supplemental Facility on January 12, 2022.
Mortgage Debt
Total mortgage indebtedness was $5.1 billion and $5.5 billion at September 30, 2023 and December 31, 2022, respectively.
Covenants
Our unsecured debt agreements contain financial covenants and other non-financial covenants. The Credit Facilities contain ongoing covenants relating to total and secured leverage to capitalization value, minimum earnings before interest, taxes, depreciation, and amortization, or EBITDA, and unencumbered EBITDA coverage requirements. Payment under the Credit Facilities can be accelerated if the Operating Partnership or Simon is subject to bankruptcy proceedings or upon the occurrence of certain other events. If we were to fail to comply with these covenants, after the expiration of the applicable cure periods, the debt maturity could be accelerated or other remedies could be sought by the lender, including adjustments to the applicable interest rate. As of September 30, 2023, we were in compliance with all covenants of our unsecured debt.