More American consumers have gotten caught up in a special brand of watchlist purgatory because their names are similar to ones on OFAC’s list of “specially designated nationals,” according to e-mails and other documents released under court order Tuesday. By law, businesses are barred from conducting transactions with anyone on the list. Tuesday’s court-ordered release of documents to the Lawyers Committee for Civil Rights of the San Francisco Bay Area, offers a window into the kinds of disruptions suffered by those ensnared in the process, as well as the difficulty of clearing their names.

More businesses are seeking, as part of a credit check, to know whether a person is also on the OFAC list. Failure to do so can bring a stiff penalty. Often a person whose name is similar to a name on the watchlist will be flagged by credit bureaus, which produce the reports businesses use to decide who is eligible for a car or home loan or to rent an apartment.

The Lawyers Committee sued the Treasury Department last year under the Freedom of Information Act for records of complaints relating to OFAC’s list. Last year, the group documented the cases of at least a dozen people denied services, including being blocked from buying exercise equipment. Tuesday’s partial release of records raised at least 30 new cases in which people sought OFAC help.

“OFAC’s list of designated individuals and entities is a powerful tool that disrupts financial flows to terrorists, narcotics traffickers and proliferators of weapons of mass destruction,” a spokesman from the Treasury, John Rankin, said. “This vigilance has an important deterrent effect and shines a light on illicit conduct.”

But the lead counsel in the group’s FOIA case, Thomas Burke, said he suspected the watchlist is causing problems for many more people than revealed by the cases so far. Moreover, he asserted, “There isn’t a program (of redress). There isn’t an ombudsman. There isn’t a procedure to help consumers clear their names.”

The president and chief executive of a credit-reporting trade group, Stuart Pratt, the Consumer Data Industry Association, said OFAC does not give adequate guidance on how to determine a watchlist match. “Do you match just on the last name, on the first name, on the first name and middle initial?” Mr. Pratt said. “OFAC doesn’t really give much guidance.”