The company saw revenue decline by 11 percent from 2020 to VND3.35 trillion, according to its financial report.
It spent VND1.62 trillion on promotions, up 22 percent, and VND303 billion on advertising, up 46 percent, as competitors like Gojek, ShopeeFood and Baemin race to attract customers via discounts.
By the end of last year Grab was recording an accumulated loss of VND4.36 trillion.
It held VND4.28 trillion in long-term debt to GrabTaxi Holdings and Grab Inc. Both loans have zero percent interest and no collateral.
Grab had recently been ordered by the Vietnam Competition and Consumer Authority to explain its "heatwave surcharge" it added earlier this month in an unprecedented move in the ride-hailing industry.
In March, the company raised fares by VND500-2,500 to help drivers cope with surging gasoline prices.