I am an architect in Denver Colorado. I have a client that has stated that they will not make the last payment without a substantial discount (after receiving all documents for City certificate for occupancy or contesting any of the work performed throughout the project until the final invoice). I originally billed them on 14 May 2019. After a back and forth through the summer we decided to reduce the invoice and billed them again 24 September as a new invoice with the itemized reduction. There has been no response . I have consultants that need to be paid and at this point I believe that I need to protect my rights. What is the best approach at this time? Steve Chucovich