In order to determine net cash provided by operating activities, net income (loss) is adjusted by, among other things, changes in current assets and current liabilities as follows (in millions):


	Nine Months Ended September 30,
	2021		2020
Decrease (increase) in current assets:
Receivables, net	$	(2,643)	$	3,229
Inventories	(232)		1,577

Prepaid expenses and other	28		70
Increase (decrease) in current liabilities:
Accounts payable	3,624		(4,893)
Accrued expenses	538		17
Taxes other than income taxes payable	200		(24)
Income taxes payable	115		(208)
Changes in current assets and current liabilities	$	1,630	$	(232)

Changes in current assets and current liabilities for the nine months ended September 30, 2021 were primarily due to the following:

•the increase in receivables was primarily due to an increase in refined petroleum product prices in September 2021 compared to December 2020 combined with an increase in refined petroleum product sales volumes, partially offset by a decrease in income taxes receivable associated with the receipt of a $962 million refund related to our U.S federal income tax return for 2020;

•the increase in accounts payable was primarily due to an increase in crude oil and other feedstock prices in September 2021 compared to December 2020 combined with an increase in crude oil and other feedstock volumes purchased; and

•the increase in accrued expenses was primarily due to an increase in our environmental credit obligations under fixed-price contracts that resulted from higher prices for Renewable Identification Numbers (RINs) in September 2021 compared to December 2020.

Changes in current assets and current liabilities for the nine months ended September 30, 2020 were primarily due to the following:

•the decrease in receivables was due to (i) a decrease of $3.6 billion as a result of a decrease in sales volumes combined with a decrease in refined petroleum product prices in September 2020 compared to December 2019 and (ii) the collection of $449 million for a blender’s tax credit receivable attributable to volumes blended during 2019 and 2018, partially offset by an increase in income taxes receivable of $770 million primarily due to the recognition of a current income tax benefit;

•the decrease in inventories was primarily due to lower inventory levels in September 2020 compared to December 2019; and

•the decrease in accounts payable was due to a decrease in crude oil and other feedstock volumes purchased combined with a decrease in crude oil and other feedstock prices in September 2020 compared to December 2019.


	Nine Months Ended September 30,
	2021		2020
Interest paid in excess of amount capitalized, including interest on finance leases	$	397	$	338
Income taxes paid (refunded), net	(876)		206

Supplemental cash flow information related to our operating and finance leases was as follows (in millions):


	Nine Months Ended September 30,
	2021				2020
	Operating Leases		Finance Leases		Operating Leases		Finance Leases
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows	$	296	$	53	$	329	$	74
Investing cash flows	1		—		1		—
Financing cash flows	—		97		—		51
Changes in lease balances resulting from new and modified leases (a)	366		93		211		1,506

(a)Noncash activity for the nine months ended September 30, 2020 primarily included $1.4 billion for a finance lease right-of-use asset and related liability recognized in connection with the terminaling agreement with MVP.

There were no significant noncash investing and financing activities during the nine months ended September 30, 2021 and 2020, except as noted in the table above.