First I'll offer you learn from the experience. 1. "I did not have a concrete statement of work because..." This was your mistake and there's really no good e

First I'll offer you learn from the experience. 1. "I did not have a concrete statement of work because..." This was your mistake and there's really no good excuse for it. The lesson here is always spell out exactly what you are going to do. 2. "The data was several GB and it wasn't clean per se." You should have alerted them to this issue as soon as you found it. Had you provided a detailed statement of work there'd be no disputing that cleaning the data was outside your scope of work. 3. "I did my job according to their proposed scope". If the data you were working was never clearly defined there's a fuzziness as to what that scope was. They, it would seem, expected you to clean the data. If they provided a sample of the data you'd be working with that didn't have any noise in it you may have some ground to stand on if you took them to court, but that's probably still not very solid ground to stand on in court if, in discussion, they implied it wasn't really a "sample" as opposed to a "rough example". At some point, if the work order was clear, you should have informed them you were having issues parsing the raw data because it was not what they described. If you did that it would help your argument. All that said, they were paying you a premium to get it right in the time allotted and you didn't deliver. Sometimes you have to suck it up and take the hit and learn from it. This may be one of those times because of #1.