The Navajo Tribe will post a $30 million budget deficit when fiscal 1988 ends on Sept. 30, financial statements presented to the tribe's Budget and Finance Committee this week indicate.

Net revenues are projected to be $98 million by Sept. 30, and the general fund expenditures and encumbrances will be $128 million, according to the statements.As of July 1, the tribe's net revenues were about $74 million and its general fund expenditures and encumbrances were about $112 million, the statements said.

The unaudited net worth of the tribe, as of July 1, stands at $291 million, the financial statements indicated. Those figures include a $70 million general fund, a $180 million special revenue fund and a $113 million fiduciary fund.

Tribal law requires that reserves, which are a part of the general fund, be kept at a minimum of $56 million. The balance of the unaudited reserves, as of July 1, is $3 million, the statements indicated.

The reserve's audited balance on Sept. 30, 1986, was $98 million but dropped to $41 million a year later.

Tribal trust funds, which require a two-thirds vote by the Navajo people to spend the principal, have grown from $16 million in September 1984 to $113 million, as of July 1.