Transaction costs
Transaction costs were $30.4 million for the three months ended September 30, 2023, an increase of $2.4 million, or 9%, compared to the prior-year period, partially due to an increase in capital advance costs of $0.8 million driven by an increase in losses recognized. Excluding the impact of these non-volume related costs, transaction costs increased by $1.6 million or 6%, while volume increased by 11% compared to the prior year period. Transaction costs grew at a lower rate than volume due to improved commercial terms with banking and other providers, internal platform optimizations, and cost structure benefits from increased transaction volume.
Transaction costs were $86.0 million for the nine months ended September 30, 2023, an increase of $6.2 million, or 8%, compared to the prior-year period, primarily due to an increase of $2.9 million in card network fees, $2.7 million in capital advance costs and $2.1 million in bank and processor fees.
Other operating expenses
Other operating expenses were $40.3 million for the three months ended September 30, 2023, an increase of $2.6 million, or 7%, compared to the prior-year period, driven by an increase of $3.3 million in third-party contract and consulting expenses and an increase of $1.0 million in information technology expenses, partially offset by a decrease of $1.0 million in employee compensation, benefits and other employee-related expenses in line with a decrease in employee headcount.
Other operating expenses were $120.9 million for the nine months ended September 30, 2023, an increase of $13.0 million, or 12%, compared to the prior-year period, driven by an increase of $10.2 million in third-party contract and consulting expenses, an increase of $3.6 million in information technology expenses, and an increase of $1.7 million in employee compensation, benefits and other employee-related expenses.
Research and development expenses
Research and development expenses were $27.0 million for the three months ended September 30, 2023, a decrease of $2.7 million, or 9%, compared to the prior-year period, driven by an increase in the capitalization of employee compensation costs related to ongoing investments in our platform infrastructure, resulting in an additional $5.0 million in capitalized costs, offset by an increase of $1.7 million in information technology expenses and $1.6 million in costs related to the workforce reduction plan discussed in the key developments and trends section.
Research and development expenses were $84.2 million for the nine months ended September 30, 2023, an increase of $2.1 million, or 3%, compared to the prior-year period, driven by an increase of $3.0 million in information technology expenses and $1.6 million in severance related costs related to the workforce reduction plan discussed above, partially offset by a decrease of $2.3 million in employee compensation, benefits and other employee-related expenses as a result of an increase in capitalization due to shifting of resources towards new investments in our platform.
Sales and marketing expenses
Sales and marketing expenses were $48.7 million for the three months ended September 30, 2023, an increase of $7.6 million, or 18%, compared to the prior-year period, driven by an increase of $6.1 million in marketplace partner commissions and $2.0 million in costs related to the previously discussed workforce reduction plan. These increases were offset by a decrease of $1.3 million in employee compensation, benefits and other employee-related expenses.
Sales and marketing expenses were $144.9 million for the nine months ended September 30, 2023, an increase of $32.5 million, or 29%, compared to the prior-year period, driven by an increase of $15.1 million in marketplace partner commissions, an increase of $9.2 million in employee compensation, benefits and other employee-related expenses as a result of an increase in average employee headcount in our sales and marketing groups as well as $2.0 million in costs associated with the previously discussed workforce reduction plan, increased spend of $3.1 million on marketing programs, and an increase of $2.9 million in third-party contractor expenses.
General and administrative expenses
General and administrative expenses were $25.1 million for the three months ended September 30, 2023, an increase of $3.4 million, or 16%, compared to the prior-year period, driven by an increase of $1.7 million in M&A and legal expenses and an increase of $1.6 million resulting from the fair value adjustment of a liability related to our 2020 acquisition of Optile that positively impacted the prior period and did not recur.