At June 30, 2021 and September 30, 2020, we had the following long-term debt obligations:

(in thousands)	June 30, 2021			September 30, 2020
4.000% Senior notes due 2028	$	500,000		$	500,000
3.625% Senior notes due 2025		500,000			500,000
Credit facility revolver⁽¹⁾		490,000			18,000
Total debt		1,490,000			1,018,000
Unamortized debt issuance costs for the senior notes⁽²⁾		(11,073	)		(12,686	)
Total debt, net of issuance costs	$	1,478,927		$	1,005,314

In February 2020, we issued $500 million in aggregate principal amount of 4.0% senior, unsecured long-term debt at par value, due in 2028 (the 2028 notes) and $500 million in aggregate principal amount of 3.625% senior, unsecured long-term debt at par value, due in 2025 (the 2025 notes).

As of June 30, 2021, the total estimated fair value of the 2028 and 2025 notes was approximately $518.3 million and $515.0 million, respectively, based on quoted prices for the notes on that date.

We were in compliance with all the covenants for all of our senior notes as of June 30, 2021.

In February 2020, we entered into a secured multi-currency bank credit facility with a syndicate of banks. We expect to use the new credit facility for general corporate purposes, including acquisitions of businesses, share repurchases and working capital requirements.

The credit facility consists of a $1 billion revolving credit facility, which may be increased by up to an additional $500 million in the aggregate if the existing or additional lenders are willing to make such increased commitments. The maturity date of the credit facility is February 13, 2025, when all remaining amounts outstanding will be due and payable. The revolving loan commitment does not require amortization of principal and may be repaid in whole or in part prior to the scheduled maturity date at our option without penalty or premium. As of June 30, 2021, the fair value of our credit facility approximates its book value.

Loans under the credit facility bear interest at variable rates which reset every 30 to 180 days depending on the rate and period selected by PTC as described below. As of June 30, 2021, the annual rate for borrowings outstanding was 1.69%. Interest rates on borrowings outstanding under the credit facility range from 1.25% to 1.75% above an adjusted LIBO rate (or an agreed successor rate) for Euro currency borrowings or range from 0.25% to 0.75% above the defined base rate (the greater of the Prime Rate, the NYFRB rate plus 0.5%, or an adjusted LIBO rate plus 1%) for base rate borrowings, in each case based upon PTC’s total leverage ratio. Additionally, PTC may borrow certain foreign currencies at rates set in the same range above the respective LIBO rates (or agreed successor rates) for those currencies, based on PTC’s total leverage ratio. A quarterly commitment fee on the undrawn portion of the credit facility is required, ranging from 0.175% to 0.30% per annum based upon PTC’s total leverage ratio.

As of June 30, 2021, we were in compliance with all financial and operating covenants of the credit facility.

We made interest payments on our debt of $3.2 million and $23.7 million in the third quarter and first nine months of 2021, respectively, and $16.4 million and $40.0 million in the third quarter and first nine months of 2020, respectively. In the third quarter of 2020, we also paid $15 million in penalties for the early redemption of the 6.000% Senior Notes due in 2024. The average interest rate on borrowings outstanding was approximately 3.1% and 3.4% during the third quarter and first nine months of 2021, respectively, and 4.0% and 4.5% during the third quarter and first nine months of 2020, respectively.