The practice has swept up dairy farmers in Maryland, an Army sergeant in Virginia saving for his children’s college education and Ms. Hinders, 67, who has borrowed money, strained her credit cards and taken out a second mortgage to keep her restaurant going.

Their money was seized under an increasingly controversial area of law known as civil asset forfeiture, which allows law enforcement agents to take property they suspect of being tied to crime even if no criminal charges are filed. Law enforcement agencies get to keep a share of whatever is forfeited.

Critics say this incentive has led to the creation of a law enforcement dragnet, with more than 100 multiagency task forces combing through bank reports, looking for accounts to seize. Under the Bank Secrecy Act, banks and other financial institutions must report cash deposits greater than $10,000. But since many criminals are aware of that requirement, banks also are supposed to report any suspicious transactions, including deposit patterns below $10,000. Last year, banks filed more than 700,000 suspicious activity reports. Owners who are caught up in structuring cases often cannot afford to fight. The median amount seized by the I.R.S. was $34,000, according to the Institute for Justice analysis, while legal costs can easily mount to $20,000 or more.

There is nothing illegal about depositing less than $10,000cash unless it is done specifically to evade the reporting requirement. But often a mere bank statement is enough for investigators to obtain a seizure warrant. In one Long Island case, the police submitted almost a year’s worth of daily deposits by a business, ranging from $5,550 to $9,910. The officer wrote in his warrant affidavit that based on his training and experience, the pattern “is consistent with structuring.” The government seized $447,000 from the business, a cash-intensive candy and cigarette distributor that has been run by one family for 27 years.

There are often legitimate business reasons for keeping deposits below $10,000, said Larry Salzman, a lawyer with the Institute for Justice who is representing Ms. Hinders and the Long Island family pro bono. For example, he said, a grocery store owner in Fraser, Mich., had an insurance policy that covered only up to $10,000 cash. When he neared the limit, he would make a deposit.

Ms. Hinders said that she did not know about the reporting requirement and that for decades, she thought she had been doing everyone a favor.