NEW YORK — On the first day of the New Year, $1.5 trillion of bank deposits will lose an unlimited government guarantee that was granted during the financial crisis to assure skittish customers their cash was safe. For a handful of boutique firms that service banks, it is a boon for business.

The accounts losing the insurance are used by businesses, municipalities, and other entities like nonprofits that are willing to forgo any interest in order to have immediate access to their large pools of cash. These accounts hold about 20 percent of all deposits in US banks. Starting Jan. 1, only $250,000 in each noninterest-bearing account will be backed by the Federal Deposit Insurance Corp.