Overall, Westchester has been closer to the mark in estimating its cash flow for items like sales-tax receipts, and its expenses for things like employee overtime.

Nassau, on the other hand, has consistently underestimated overtime costs and, at least since 1995, it has overestimated sales-tax receipts.

The corporation's more than $6.5 billion in bonds are backed by the city's sales-tax receipts, which are diverted each year to pay off the debt.

Of particular worry to many officials is the impact on retail sales and sales-tax receipts, because Wall Street salaries and bonuses might be sharply reduced.

There also is an element of an economic slowdown, particularly in sales-tax receipts, which are behind estimates in all three states.

They said an increase in the county's share of programs mandated by the state, combined with lagging sales-tax receipts, had put tremendous financial pressure on the county.

Budget Director Philip R. Michael said possible further reductions in sales-tax receipts could push the gap to $300 million.

In Suffolk the more immediate problem is making up for the shortfall that is expected in sales-tax receipts, the backbone of county budgets.

Property taxes make up only 14 percent of the county's general-fund revenues, Mr. Spero said, while sales-tax receipts, which are collected by the state, contribute nearly 42 percent.

Recent announcements that sales-tax receipts in December were $10.4 million lower than expected will only add to cost-cutting efforts at the Capitol.