For the first quarter of 2021, Trip.com Group reported net revenue of RMB4.1 billion (US$628 million), representing a 13% decrease from the same period in 2020, mainly due to a strong recovery in March 2021, partially offset by the decrease in cross-border travel. Net revenue for the first quarter of 2021 decreased by 17% from the previous quarter.
Accommodation reservation revenue for the first quarter of 2021 was RMB1.6 billion (US$241 million), representing a 37% increase from the same period in 2020, primarily due to the strong demand for inter-provincial stays. Accommodation reservation revenue for the first quarter of 2021 decreased by 30% from the previous quarter, primarily due to the travel restrictions introduced in January and February of 2021.
Transportation ticketing revenue for the first quarter of 2021 was RMB1.5 billion (US$230 million), representing a 37% decrease from the same period in 2020, and an 11% decrease from the previous quarter, primarily due to the travel restrictions introduced in January and February of 2021.
Packaged-tour revenue for the first quarter of 2021 was RMB169 million (US$26 million), representing a 68% decrease from the same period in 2020, and a 35% decrease from the previous quarter.
Corporate travel revenue for the first quarter of 2021 was RMB252 million (US$39 million), representing a 101% increase from the same period in 2020. Corporate travel revenue for the first quarter of 2021 decreased by 18% from the previous quarter.
Gross margin was 75% for the first quarter of 2021, which slightly increased from 74% for the same period in 2020. Gross margin for the first quarter of 2021 decreased from 82% for the previous quarter, largely due to the travel restrictions at the outset of 2021.
Product development expenses for the first quarter of 2021 increased by 31% to RMB2.2 billion (US$340 million) from the same period in 2020, primarily due to the fluctuations in expenses related to product development personnel. Product development expenses increased by 3% from the previous quarter. Product development expenses for the first quarter of 2021 accounted for 54% of the net revenue.
Sales and marketing expenses for the first quarter of 2021 decreased by 31% to RMB952 million (US$145 million) from the same period in 2020 and decreased by 23% from the previous quarter, primarily due to the decrease in expenses relating to sales and marketing promotion activities. Sales and marketing expenses for the first quarter of 2021 accounted for 23% of the net revenue.
General and administrative expenses for the first quarter of 2021 decreased by 65% to RMB684 million (US$104 million) from the same period in 2020, primarily due to the decrease in allowance for expected credit losses which we accrued amount of RMB1.2 billion in the first quarter of 2020. General and administrative expenses increased by 1% from the previous quarter. General and administrative expenses for the first quarter of 2021 accounted for 17% of the net revenue.
Income tax expense for the first quarter of 2021 was RMB41 million (US$6 million), compared to income tax benefit of RMB254 million in the same period of 2020 and income tax expense of RMB163 million in the previous quarter. The change in our effective tax rate was primarily due to the non-taxable income of the fair value changes in equity securities investments and exchangeable senior notes.