Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations (continued)
Marketing and sales expense
Marketing and sales expense was $127,243 and $108,140 for the three months ended June 30, 2023, and 2022, respectively. This was an increase of 17.7%. Compensation expense and travel expense increased $10,473 and $7,362, respectively, during the three months ended June 30, 2023 compared to the same period in 2022. Marketing and sales expense was $236,814 and $190,328 for the six months ended June 30, 2023, and 2022, respectively. This was an increase of 24.4%. Compensation expense and travel expense increased $27,998 and $16,587, respectively, during the six months ended June 30, 2023 compared to the same period in 2022. We increased our sales staff in May 2023, and exhibited at major international photonics trade shows during the first and second quarters of 2023.
Stock compensation expense
Included in total expenses were noncash stock-based compensation costs of $395 and $8,673 for the three months ended June 30, 2023 and 2022, respectively. Included in total expenses were noncash stock-based compensation costs of $45,485 and $31,972 for the six months ended June 30, 2023 and 2022, respectively. Compensation expense for all stock-based awards is based on the grant date fair value and recognized over the required service (vesting) period. Unrecognized non-cash stock-based compensation expense was $0 at June 30, 2023.
Interest
Interest income, net was $63,914, and $112,891 for the three and six months ended June 30, 2023, respectively. Interest expense, net was $5,769 and $12,262 for the three and six months ended June 30, 2022, respectively. The improvement was due to our approximately $2.0 million of investments in marketable securities which benefited from an overall increase in interest rates. Interest expense has decreased as we continue to reduce our debt outstanding.
Income taxes
Income tax expense was $144,346, and $83,400 for the three months ended June 30, 2023, and 2022, respectively. Income tax expense was $302,556, and $144,200 for the six months ended June 30, 2023, and 2022, respectively. The effective tax rate for the three and six months ended June 30, 2023 was 22.0% and 22.4%, respectively, compared to the tax rate of 21.7% for calendar year 2022. At December 31, 2022, the deferred tax asset was $151,164. As of each reporting date, management considers new evidence, both positive and negative, that could affect its view of the future realization of deferred tax assets. Accordingly, management determined that no valuation allowance was necessary at December 31, 2022. The deferred tax asset was $0, and the deferred tax liability was $73,828 at June 30, 2023.
Net income
Net income for the three months ended June 30, 2023, and 2022, was $511,359 and $664,873, respectively. The decrease in the second quarter was the result of lower gross profit and higher operating and income tax expenses. Net income for the six months ended June 30, 2023, and 2022, was $1,049,379, and $1,049,274, respectively.
Liquidity and Capital Resources
Cash
As of June 30, 2023, cash on hand was $5,108,113 compared to $3,947,966 at December 31, 2022 due to net cash provided by operating activities partially offset by our investment in our manufacturing footprint and acquisition of production equipment.
Working capital
At June 30, 2023, working capital was $6,491,066 compared to $5,211,625 at December 31, 2022, an increase of $1,279,441 or 24.5%. Cash increased $1,160,147, accounts receivable increased $195,085, while inventories and customer deposits decreased $480,452, and $358,729, respectively.