on could be based on higher interest rates and shorter maturities and could impose a significant burden on our results of operations and financial condition, and the issuance of additional equity securities could result in significant dilution to stockholders.
Cash Flows
Operating Activities
For the nine months ended September 30, 2022, net cash used in operating activities was approximately $5,610,000, which consisted of a net loss of approximately $8,086,000 offset by non-cash charges of approximately $1,829,000, which included $826,000 related to amortization of internally developed software, $633,000 in stock-based compensation, $341,000 in bad debt expense, $14,000 related to depreciation and amortization of property and equipment, $9,000 of amortization of debt issuance cost on the Term Loan, and $6,000 of proceeds from issuance of common stock in exchange for services. Total changes in assets and liabilities of approximately $647,000 were attributable to a $877,000 decrease in accounts receivable-unbilled, a $443,000 decrease in accounts receivable, a $135,000 increase in accounts payable, offset by a $655,000 decrease in deferred revenue, a $124,000 decrease in accrued expenses, and a $15,000 increase in prepaid expenses and other current assets.
For the nine months ended September 30, 2021, net cash used in operating activities was $9,349,000, which consisted of a net loss of $6,911,000 offset by non-cash charges of approximately $3,019,000, which primarily includes a $2,740,000 loss on extinguishment of bridge notes, $870,000 of amortization of discount on amended bridge notes, $714,000 related to amortization of internally developed software, a $260,000 loss on extinguishment of convertible notes, $450,000 in stock based compensation, $34,000 in bad debt expense, $33,000 related to depreciation and amortization of property and equipment, $13,000 proceeds from issuance of common stock in exchange for services, $3,000 of amortization of debt issuance cost on the Term Loan, and $1,000 of amortization of discount and debt issuance costs on convertible notes, partially offset by a $1,312,000 loss on derivative liabilities, and a $788,000 gain on the extinguishment of the note payable. Total changes in assets and liabilities of approximately $5,456,000 were primarily driven by a $1,710,000 decrease in accrued interest, a $1,441,000 decrease in accounts payable, a $1,226,000 increase in accounts receivable, a $1,098,000 increase in accounts receivable-unbilled, a $155,000 decrease in deferred revenue, and a $41,000 increase in prepaid expenses and other current assets, partially offset by an increase in accrued expenses of $214,000.
Investing Activities
Net cash used in investing activities was approximately $1,549,000 and $734,000 for the nine months ended September 30, 2022 and 2021, respectively. Net cash used in investing activities for the nine months ended September 30, 2022 consisted of $1,549,281 of capitalization of internally developed software. Net cash used in investing activities for the nine months ended September 30, 2021 consisted of $731,172 of capitalization of internally developed software and $2,550 for purchases of property and equipment.
Financing Activities
Net cash provided by financing activities was approximately $78,000 and $19,200,000 for the nine months ended September 30, 2022 and 2021, respectively. Net cash provided by financing activities for the nine months ended September 30, 2022 consist of $78,387 received from the exercise of stock options. Net cash provided by financing activities for the nine months ended September 30, 2021 consisted of $18,000,000 of proceeds received from the issuance of common stock in connection with the IPO, $3,500,000 of proceeds received from the issuance of note payable, $2,498,000 of proceeds from the issuance of over-allotment shares of common stock, $500,000 of proceeds received from the issuance of bridge notes payable, $44,000 of proceeds received from the exercise of stock options, and $1,000 of proceeds received from the exercise of warrants, partially offset by the $3,000,000 payment of principal to the holders of the bridge notes, $2,340,000 for the payment of offering costs in connection with the issuance of common stock in connection with the IPO, and $26,000 for the payment of debt issuance costs in connection with the note payable.
Effects of Inflation and Supply Chain Shortages
Our operations are heavily reliant on specimen availability, and as a result, we often receive more requests than we can fulfill. While the Company is subject to these types of supply chain constraints that are specific to the specimen industry, we have not been affected by the more common supply chain issues currently affecting the economy, specifically surrounding transportation. Due to the small size of the packages that we ship, our carriers were able to continue making timely deliveries during the nine months ended September 30, 2022.