associated with the previously mentioned reserves that were recorded in 2020. For the nine months ended September 30, 2020 and 2019, we received cash distributions from the PEs of $424,000 and $888,000, respectively.
Interest expense, net
Interest expense, net was $285,000 and $62,000 for the three months ended September 30, 2020 and 2019, respectively. Interest expense, net was $783,000 and $163,000 for the nine months ended September 30, 2020 and 2019, respectively. The increase in interest expense, net is primarily due to the issuance of convertible debt from November 2019 through April 2020 and higher bank indebtedness balances during 2020 as compared to 2019.
Income Tax Expense
For the three and nine months ended September 30, 2020, we recorded income tax benefits of $367,000 and $2,396,000, respectively. The income tax benefit was recorded to the extent of previously recorded deferred tax liabilities, but not to the extent to create a deferred tax asset as utilization of that asset in future periods is not reasonably assured. For the three and nine months ended September 30, 2019, we recorded income tax expense of $1,094,000 and $3,022,000, respectively. Our estimated annual tax rate is impacted primarily by the amount of taxable income earned in each jurisdiction we operate in, changes in deferred tax assets and liabilities, and to permanent differences between financial statement carrying amounts and the tax basis.
LIQUIDITY AND CAPITAL RESOURCES
For the years ended December 31, 2019 and 2018
Our cash position at December 31, 2019 was $59,000 compared to the December 31, 2018 cash balance of $831,000. Working capital was $22,106,000 as of December 31, 2019 compared to $22,294,000, at December 31, 2018, largely on the basis of an increase of approximately of $8,688,000 in net accounts receivables, partially offset by an increase in current liabilities of $7,838,000. We rely on payments from multiple private insurers and hospital systems that have payment policies and payment cycles that vary widely. Because we are primarily an out-of-network biller to private insurance companies, the collection times for our claims can last in excess of 24 months.
For the year ended December 31, 2019, we collected approximately $6,865,000 of cash from its accounts receivable balance compared to collecting approximately $5,552,000 in the same prior year period despite the carrying amount of accounts receivable increasing. We had $979,000 of cash distributions from its PE entities for the year ended December 31, 2019 compared to $1,171,000 for the same prior year period.
We financed our operations primarily from revenues generated from services rendered and through equity and debt financings. We expects to meet our short-term obligations, through cash earned through operating activities, debt financings, issuances of convertible debentures and stock sales. As of December 31, 2019, we had drawn the full amount on its banking line of credit.
Cash used in operating activities for the year ended December 31, 2019 was $4,228,000 compared to cash used in operating activities of $361,000 for the same period in the preceding year. Cash was used to fund working capital increases primarily in accounts receivable related to our growth.
Cash provided by investing activities of $465,000 and $875,000 for the years ended December 31, 2019 and 2018, respectively, was primarily due to distributions received from equity method investments. On May 29, 2019, we acquired the net assets, primarily consisting of accounts receivable, of Littleton Professional Reading for $700,000. Of this amount $466,000 was paid during the year ended December 31, 2019 and the remainder is due prior to the end of 2020. Through May 15, 2020, we collected approximately $700,000 of cash from the accounts receivable acquired in the Littleton Professional Reading acquisition.
Cash provided by financing activities of $2,991,000 for the year ended December 31, 2019 was primarily due to net proceeds from our bank promissory note and line of credit, proceeds from the issuance of convertible debentures, and proceeds from a sale-leaseback transaction, offset by payments associated with lease liabilities