The budget includes expenditure of $36.5 billion, up 4.5 percent from 2014, and revenue of $30.03 billion, down 1.0 percent, the official ONA news agency cited the finance ministry as saying.
The projected deficit will represent 21 percent of public revenue and 8.0 percent of the sultanate's GDP.
Oman is a small producer of crude, at about one million barrels per day.
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Current expenditure accounts for the lion's share at 68 percent of public spending, far ahead of investments (23 percent), the ministry said.
Because of the falling price of oil -- which brings in 79 percent of Muscat's revenues -- the government had to "take preventative measures... to preserve financial and economic stability", the ministry's statement said.
However, these "would have no impact" on the standard of living or on social services and employment, it added.
The statement said subsidies on consumer goods and social services in the new budget would account for 8.0 percent of public expenditure in 2015.