I have a wage garnishment through a court order I have paid all except about 250 dollars they say that I owe 900 I have my paycheck stubs can they charge me interest overtop the amount that the court records state owed

Are you in the U.S. I have been in accounting for over 20 years and they always send paper work which can easily be disputed or worked with. If you are U.S. check your paper work, there is a phone number and most circumstances only take a phone call to clear things up or change the amount you are paying.

You paid all except 250 of what figure, the original amount,
In the US, yes, they will be getting interest.

From the original amount you owed, there would be legal fees, court fees and interest added