expenses was primarily offset by an increase in professional fees. Selling, general and administrative expenses included stock-based compensation expense of $205,000 and $262,000 for the three months ended December 31, 2019 and 2020, respectively. Selling, general and administrative expenses were unchanged at $8.1 million in the nine months ended December 31, 2019 and in the nine months ended December 31, 2020. Decreases in independent sales representative commissions of $466,000 and $131,000 in travel expenses were primarily offset by increases in professional fees, payroll related expenses and stock-based compensation expense. Selling, general and administrative expenses included stock-based compensation expense of $595,000 and $732,000 for the nine months ended December 31, 2019 and 2020, respectively.
Interest Income and Other Income, Net. Interest and other income, net decreased 87.9% from income of $207,000 in the three months ended December 31, 2019 to $25,000 in the three months ended December 31, 2020. Interest income decreased by $139,000 primarily due to lower interest rates received on our cash and short-term and long-term investments. Foreign exchange gains were $18,000 for the three months ended December 31, 2019 compared to losses of $25,000 for the three months ended December 31, 2020. The exchange gains and losses in each period were related to our Taiwan branch operations and our operations in Israel. Interest and other income, net decreased 79.6% from income of $564,000 in the nine months ended December 31, 2019 to $115,000 in the nine months ended December 31, 2020. Interest income decreased by $366,000 primarily due to lower interest rates received on our cash and short-term and long-term investments. We had a foreign exchange loss of $46,000 for the nine months ended December 31, 2019 compared to $129,000 for the nine months ended December 31, 2020. The exchange losses in each period were related to our Taiwan branch operations and our operations in Israel.
Provision for Income Taxes. The provision for income taxes increased 7.1% from $84,000 in the three months ended December 31, 2019 to $90,000 in the three months ended December 31, 2020 and increased 251.1% from $182,000 in the nine months ended December 31, 2019 to $639,000 in the nine months ended December 31, 2020. This change for the nine month period was primarily due to the settlement of an income tax audit in Israel during the quarter ended June 30, 2020 for fiscal years 2016 through fiscal 2019 which resulted in a discrete tax provision of $479,000, and to a lesser extent due to fluctuations in the relative mix of income among our operating jurisdictions.
Net Loss. Net loss was $4.6 million in the three months ended December 31, 2019 compared $5.2 million in the three months ended December 31, 2020 and was $6.5 million in the nine months ended December 31, 2019 compared to $16.5 million in the nine months ended December 31, 2020. These fluctuations were primarily due to the changes in net revenues, gross profit and operating expenses discussed above.
Liquidity and Capital Resources
As of December 31, 2020, our principal sources of liquidity were cash, cash equivalents and short-term investments of $52.3 million compared to $66.6 million as of March 31, 2020.
Net cash used in operating activities was $11.4 million for the nine months ended December 31, 2020 compared to $1.2 million for the nine months ended December 31, 2019. The primary uses of cash in the nine months ended December 31, 2020 was the net loss of $16.5 million and a reduction in accrued expenses and other liabilities of $1.7 million. The reduction in accrued expenses and other liabilities was primarily related to the payment of fiscal 2020 year-end accruals for purchased intellectual property. Primary sources of cash in the nine months ended December 31, 2020 were a reduction in accounts receivable of $2.3 million, non-cash items including stock-based compensation of $2.1 million and depreciation and amortization expenses of $962,000 and an increase in accounts payable of $1.2 million. The decrease in accounts receivable was primarily due to the decrease in shipments in the quarter ended December 31, 2020 compared to the quarter ended March 31, 2020.
The primary uses of cash in the nine months ended December 31, 2019 was the net loss of $6.5 million, an increase of $1.1 million in prepaid expenses and other assets and a reduction in accounts payable of $728,000.
Primary sources of cash in the nine months ended December 31, 2019 were non-cash items including stock-based compensation of $1.9 million and depreciation and amortization expenses of $1.1 million and a reduction in accounts receivable of $2.0 million. The decrease in accounts receivable was primarily due to the decrease in net revenues in the quarter ended December 31, 2019 compared to the quarter ended March 31, 2019.