I am an independent contractor and do consulting work for a number of companies at any given time. When the one company submitted the 2016 IRP5 they erroneously categorized my source code as 3601, instead of 3616 for independent contractors, hence I cannot claim costs. I have asked them to amend the IRP5 but they say they cannot because they have finished their tax recon and signed off on 2016 and can no longer make changes. Is this true? What alternatives do I have?