At March 31, 2023, we carried a total debt balance (including accrued interest) of €6,565.4 million, of which €1,460.0 million principal amount is related to the € and USD-denominated Senior Secured Fixed Rate Notes due March 2028 and €3,221.4 million principal amount is owed under our 2020 Amended Senior Credit Facility with maturities ranging from April 2028 through April 2029. Our total debt balance at March 31, 2023 also included outstanding liabilities of €391.5 million related to the mobile spectrum licenses following last year's multiband spectrum auction as we have opted for annual deferred payments over the lifetime of each license as opposed to advance payments. Furthermore, our total debt balance at March 31, 2023 reflected a principal amount of €321.3 million related to our vendor financing program as further detailed below. The remainder primarily represents lease obligations associated with (i) the June 1, 2022 sale of our mobile tower business to DigitalBridge resulting into a 15-year MLA as further detailed above, (ii) the long-term emphyotic lease with Fluvius for the use of its HFC network covering approximately one-third of Flanders prior to the anticipated closing of the NetCo transaction which we expect by summer this year and (iii) other leases.
At March 31, 2023, we carried €321.3 million of short-term debt related to our vendor financing program, all of which is maturing within less than twelve months and which carries a margin of 195 basis points over EURIBOR (floored at 0%). Relative to December 31, 2022, the outstanding short-term vendor financing liabilities declined €24.6 million in Q1 2023, reflecting seasonality in some of our scheduled vendor financing payments and negatively impacting our Adjusted Free Cash Flow by the same amount in the quarter. We anticipate a broadly stable evolution in 2023 compared to December 31, 2022, as embedded in our FY 2023 Adjusted Free Cash Flow outlook, yet with a certain seasonality in some of our payments from quarter to quarter.
Except for our vendor financing and mobile spectrum commitments, all of our floating interest rate and foreign exchange currency risks have been hedged until the maturity of such debt instruments through a series of derivatives, improving the visibility on our future Adjusted Free Cash Flow and minimizing exposure to financial market fluctuations. Excluding short-term liabilities related to our vendor financing program, we face no debt maturities prior to March 2028 with a weighted average maturity of approximately 5.3 years at March 31, 2023. Our weighted average cost of debt at March 31, 2023, including hedges, was approximately 3.1%, excluding commitment fees, leases, vendor financing and amounts related to mobile spectrum licenses. Finally, we also had full access to €555.0 million of undrawn commitments under our revolving credit facilities at March 31, 2023, with certain availabilities up to September 2026.
For more information on our debt instruments and payment schedule at March 31, 2023, we refer to the Q1 2023 Investor & Analyst Toolkit.