General and administrative costs for the nine months ended September 30, 2020 decreased by $276,065 or 5% as compared to the same period in 2019. This reduction in costs was due to the following factors: a decrease in legal fees of $284,128; a decrease in IT and security consulting fees of $150,000; and a decrease in travel related expenses of $109,104 partially offset by a net increase in salary and stock-based compensation expenses of $156,173. The net increase here was a reduction in cash salaries paid of $478,301, offset by an increase of $634,474 in stock-based compensation, which resulted from the voluntary salary reduction program that the Company implemented in May 2020; and an increase in insurance premiums of $80,747.
Depreciation and Amortization. Depreciation and amortization expense for the nine months ended September 30, 2020 was $1,923,922 as compared to $1,795,782 in the same period in 2019, an increase of $128,140. The increase in depreciation expense is due to new investments in depreciable assets, including manufacturing equipment and molds placed into service from construction-in-progress and leasehold improvements associated with our plant expansion which were completed in the first quarter of 2019.
Other Income (Expense). Total other expense, net was $35,758 for the nine months ended September 30, 2020 as compared to income of $48,539 in the period in 2019. The overall increase of $84,297 in other expenses was primarily the result of a decrease of $149,148 in investment interest income, which is dependent upon average cash balances over the period, partially offset by a decrease of $45,837 in other taxes.
Provision for Income Taxes. There was not a provision for income taxes in the respective six-month periods ending September 30, 2020 and 2019.
Liquidity and Capital Resources
As of September 30, 2020, we had cash and cash equivalents of $24,938,858, an increase of $14,332,767 from $10,606,091 as of December 31, 2019.
As of September 30, 2020, we had current assets of $34,217,465 as compared to current liabilities of $3,257,792 which resulted in a positive working capital position of $30,959,673. As of December 31, 2019, we had a working capital position of $16,438,851. Our current liabilities are comprised principally of accounts payable, current portion of debt, accrued expenses and operating lease right-of-use liabilities.
During the nine months ended September 30, 2020, we used $11,259,877 of cash for operating activities as compared to $18,051,495 for the comparable period in 2019. For the nine months ended September 30, 2020 we incurred a net loss of $14,361,100, partially offset by non-cash operating expenses of $4,153,956, for a net cash loss of $10,207,144. Net changes in working capital items were $1,052,733 for the 2020 period with the largest factor resulting from $784,077 expenditures in inventory and vendor prepayments for M400 components.
For the three months ended September 30, 2020, net loss after adding back non-cash operating expenses, such as depreciation and amortization, stock-based compensation and impairment of patents and trademarks, was $2,987,236 versus $4,493,345 in the same period of 2019. The net loss after adding back non-cash operating expenses was $10,207,144 for the nine months ended September 30, 2020 versus $13,819,736 for the same period of 2019.
During the nine months ended September 30, 2020, we used $1,162,592 of cash for investing activities, which includes $467,595 for purchases of manufacturing equipment and product mold tooling, $365,650 in the purchase of software operating system license upgrades for our smart glasses platform, and $329,347 of investments in patents and trademarks. For the nine months ended September 30, 2019, we used a total of $2,426,549 in cash for investing activities.
During the nine months ended September 30, 2020, we received $26,755,236 in cash from financing activities, which included; (i) $10,582,309 in net proceeds from our sale of equity securities that closed on May 13, 2020, (ii) $1,555,900 in proceeds from the term loan obtained under the Payroll Protection Act, and (iii) $14,617,027 in net proceeds from our sale of equity securities that closed on September 9, 2020. For the nine months ended September 30, 2019, we received $18,855,007 from financing activities.