Hello, I just recently built a house in Texas. To keep it simple, we found a contractor we liked and vetted and paid them to build our house. At the end of the building, we were happy with the work they had done and payed the final installment. About 8 months later we are discussing with our CPA about making tax write-offs since we are using it as a business. He agrees we can make tax write-offs for certain expenses. We (he) examine the books and realize we were double-billed for certain building materials for the house. The total double-billed was around $35,000. My question is how do we go forward with this to get our over-billed money back? Thank you very much!