Hundreds gathered around City Hall on Tuesday to argue that Mayor Bloomberg’s proposed budget cuts don’t add up—because there’s already ample money in the city’s coffers to close this year’s funding gap, and could be even more.

The mayor’s executive budget, released on May 6, proposed $400 million in budget cuts, resulting in proposed layoffs of teachers, social workers, librarians and health care professionals. Bloomberg blamed the cuts on reduced state aid to the city. This week, the city and municipal unions have been talking about tapping into a union healthcare reserve fund to avoid layoffs. But for now, they are still on the table.

According to those who rallied Tuesday, they need not be, because the city will actually roll $3.6 billion in surplus funds from this year into fiscal 2012.

City Hall says that money is needed to close next year’s budget gap.

There might be even more money available to close the gap. The organizers of Tuesday’s march, DC37, released a report claiming that the city has been failing to collect over $848 million in tax revenue, from things such as cell phone towers, billboards and tax-exempt properties under new ownership.

In the past 10 years, tax breaks have increased by 182 percent, from less than $1 billion to $2.6 billion, the union claimed. One alleged instance of money failing to be collected is tax exempt, multi-million dollar homes being purchased by wealthy individuals, who then fail to notify the Department of Finance of the building’s new ownership. The property remains untaxed while the city loses out on millions of dollars and multi-millionaires reap the benefits.

Of the approximately 9,000 cell phone towers in New York, only 3,000 of them are generating collected revenue, the union said, because the Department of Finance, the employees of which are responsible for collecting this money, are themselves seeing their ranks cut through layoffs and attritions. This essentially means that because there are fewer workers available to collect revenue from these towers, and that as a result even more workers will ultimately be cut.

“He likes to do this,” said Zita Allen, Director of Communications at the DC37, said of the mayor. “There is no budget deficit. They’re just throwing money away, and not collecting the money that’s owed to them.”

The rally pulled in representatives from the spectrum of municipal workers. Among them was the Local 1321 Queens Library Guild, whose workers have already seen 234 layoffs since the budget was released, according to John Hyslop, the president of Local 1321. He says if the cuts go through, they could see additional layoffs of up to 400 people.

The Uniformed Sanitationmen’s Association also had a large presence. “We haven’t seen any layoffs yet,” one member said. “But we’re no fools. If they’re willing to fire teachers, they definitely won’t have any remorse when it comes to us. We just don’t trust the mayor anymore. His agenda is not the working man’s agenda.”

Selwyn Barrington, a food and nutrition worker, said that he has seen several layoffs so far, and thinks that it is just the beginning.

“They need to cut this out,” he said. “You have some men working five hours per day. You can barely expect him to pay rent and survive off that, much less survive without it.”