were negatively impacted in the period ended December 31, 2022, principally due to increases in the cost of certain electronic components and due to the mix of products sold.
Expenses. Selling, general and administrative expenses were $1,178,502 for the three months ended December 31, 2022, compared to $1,569,746 for the comparable three months in the prior year. As a percentage of net sales, these expenses decreased to 20.5% for the three-month period ended December 31, 2022, from 29.5% for the 2021 period. These expenses decreased as a percentage of net sales principally due to a reduction in salaries expense, a reduction in legal and consulting expenditures related to the potential merger, and a reduction in freight, and other selling expenditures.
Research and development expenses were comparable at $101,670 for the three-month period ended December 31, 2022, to $97,370 for the comparable quarter of the prior year.
Interest Expense. Our interest expense was $76,755 for the quarter ended September 30, 2022, compared to interest expense of $14,156 for the quarter ended December 31, 2021. Interest expense is dependent upon the total amounts borrowed from the Factor and the increase in interest rates during the period as compared to the corresponding period of the prior year.
Net Income. We reported net income of $341,312 for the quarter ended December 31, 2022, compared to a net income of $35,351 for the corresponding quarter of the prior fiscal year, a $305,961 (865.5%) increase in net income. The primary reasons for the increase in the net income is supply chain disruptions have begun to abate resulting in higher sales and due to reduced selling, general, and administrative expense as described above.
Nine Months Ended December 31, 2022 and 2021
Sales. Net sales for the nine months ended December 31, 2022, were $16,251,106 compared to $15,259,235 for the comparable nine months in the prior period, an increase of $991,871 (6.5%). Sales increased principally due to the Company’s ability to fill orders as delays in unloading inventory at California ports of entry began to abate during the period.
Gross Profit Margin. The gross profit margin is calculated as net sales less cost of goods sold expressed as a percentage of net sales. The Company’s gross profit margin was 28.8% for the period ended December 31, 2022, and 29.8% for the period ended December 31, 2021. Gross margins were negatively impacted in the nine-month period ended December 31, 2022, principally due to increases in the cost of certain electronic components and due to the mix of products sold.
Expenses. Selling, general and administrative expenses were $3,750,348 for the nine months ended December 31, 2022, compared to $4,059,988 for the comparable nine months in the prior year. As a percentage of sales, these expenses were 23.1% for the nine-month period ended December 31, 2022, and 26.6% for the comparable 2021 period. These expenses decreased as a percentage of net sales principally due to a reduction in salaries expense resulting from recording an employee retention credit of $181,000 under the CARES Act, and a reduction in work force. These expenses also decreased due to a reduction in legal and consulting expenditures related to the potential merger.
Research and development expenses were comparable at $294,177 for the nine months ended December 31, 2022, to $295,496 for the comparable period of the prior year.
Interest Expense. Our interest expense was $200,776 for the nine months ended December 31, 2022, compared to interest expense of $37,954 for the nine months ended December 31, 2021. Interest expense is dependent upon the total amounts borrowed from the Factor and the increase in interest rates during the period as compared to the corresponding period of the prior year.
Net Income. We reported net income of $435,776 for the nine months ended December 31, 2022, compared to a net income of $157,688 for the corresponding period of the prior fiscal year, an increase in the net income of $278,088 (176.4%). The primary reasons for the increase in the net income is supply chain disruptions have begun to abate resulting in higher sales. In addition, the Company recorded a reduction in salaries expense resulting from an Employee Retention Credit under the provisions of the Coronavirus Aid Relief, and Economic Security Act, and due to reduced selling, general, and administrative expense as described above.