Unsupported use of WITH clause

Summary:

My custom report is producing the error of Unsupported use of WITH clause

Content (please ensure you mask any confidential information):

I have developed a report starting off with the WITH YTD_BUDGET AS and continuting until I have all my pieces of data. However after careful analysis of the results it became clear that although the code combinations were pulling through, its related dff's were not. The reason for it is as there are no actuals on the GL_BALANCES table The dff's information are on the gl_code_combinations but cant get joined.

Hence I thought a full outer join would be best. Refer updated code section in attachment. If I run the code for just the YTD_ACTUAL part it pulls the data correctly, but inserting it into the main code produces an error of Unsupported use of WITH clause.