You collect on a judgment by using the various collection techniques through the legal system. These include a Motion for Garnishment, which can be used to take a bank account, garnish wages, essentially take possession of anything that would be equivalent to cash being held by another.
You can also use an Application for Writ of Execution which orders the Sheriff to seize non-exempt property of the debtor. That property is then sold at auction, after a time, and the sheriff's fees paid out of the amount and the remainder, up to what you are owed is paid to you. The rest, if it is in excess of what is owed, is given to the debtor.
However, collecting on a judgment is exponentially harder than getting a judgment in the first place. Most people choose to hire a debt collection agency or a debt collection lawyer to assist them with this and pay them by the hour or a percentage. One of the problems a creditor has to be careful of if they are trying to do this themselves is seizing property that really isn't allowed to be seized. An example of this would be seizing a bank account that only has money in it from Social Security Disability. The creditor would be ordered to return the money to the debtor and, in addition, could be ordered to pay damages since Social Security funds are exempt from seizure except for debts to the government and child support.
These are the main ways to collect on a judgment.
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