Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations (continued)
Marketing and sales expense
Marketing and sales expense was $109,571 and $82,188 for the three months ended March 31, 2023, and 2022, respectively. This was an increase of 33.3%. Compensation expense and travel expense increased $17,525 and $9,225 during the three months ended March 31, 2023, and 2022, respectively. We exhibited at a major international photonics trade show for the first time during the first quarter of 2023.
Stock compensation expense
Included in total expenses were noncash stock-based compensation costs of $45,090 and $23,299 for the three months ended March 31, 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 $394 as of March 31, 2023 and will be recognized through April of 2023.
Interest
Interest income was $48,977, for the three months ended March 31, 2023. Interest expense was $6,493 for the three months ended March 31, 2022. The improvement was due to our approximately $2.0 million investment in marketable securities and the overall increase in interest rates. Interest expense has decreased as we continue to reduce our debt outstanding.
Income taxes
Income tax expense was $158,210, and $60,800 for the three months ended March 31, 2023, and 2022, respectively. 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, and the deferred tax asset was $34,231 at March 31, 2023.
Net income
Net income for the three months ended March 31, 2023, and 2022, was $538,020, and $384,401, respectively. The increase was primarily the result of higher revenue, gross profit and interest income partially offset by higher operating and income tax expenses.
Liquidity and Capital Resources
Cash
As of March 31, 2023, cash on hand was $4,495,169 compared to $3,947,966 at December 31, 2022 due to net cash provided by operating activities in conjunction with investment in our manufacturing footprint and acquisition of production equipment.
Working capital
At March 31, 2023, working capital was $5,843,578 compared to $5,211,625 at December 31, 2022, an increase of $631,953 or 12.1%. Cash increased $547,203, inventories increased $441,214, prepaid expenses increased $200,093 and customer deposits increased $823,495 while accounts payable decreased $198,002.