A recovery in prices in April was not enough to prevent a sharp fall in Vietnam's oil revenues.
The Ministry of Finance's new data showed a year-on-year drop of 48.1 percent to VND13 trillion (US$576.71 million) in the first four months. That was equivalent to less than 24 percent of the target.
The decline happened even as the average price of Vietnam's crude oil increased 18 percent month-on-month to around $39 per barrel in April, according to the ministry.
Export and import tariff revenues, another main income source of the state budget, also declined 15.9 percent to VND38.9 trillion in January-April, it said.
However, the state's revenue still posted a slight increase of 1.2 percent to VND317 trillion in the first four months, as other sources such as corporate and luxury taxes grew 9.6 percent compared to the same period last year.
Spending increased 4.7 percent to more than VND370.6 trillion, the ministry reported.
More than 70 percent of the spending was for funding the government's administrative system, while public projects such as transport infrastructure and schools accounted for just around 15 percent.
Vietnam's debt servicing costs grew 4.4 percent to VND51.9 trillion in January-April, or 15 percent of the state spending.
Latest figures released by the government in March showed Vietnam's public debt was equivalent to 62.2 percent of GDP, and foreign debt 43.1 percent.
Vietnam's legislature capped the state budget deficit 4.95 percent of gross domestic product this year.
Last year the budget deficit was originally expected to be around 5 percent of GDP, but in the end it was equivalent to 6.1 percent.