This is a classical problem of loading multiple Fact tables (Sales and Budget, in your case) into a single Qlik document. When multiple facts have a number of common dimensions, they usually cause Synthetic keys and sometimes even Circular References.
These problems are solved with Data Modeling techniques. The two most commonly used models are Link Tables and Concatenated Facts. You can find plenty of free documents on this site that describe these two models. You can also consider reading my new book QlikView Your Business, where I'm describing in detail how to build Link Tables and Concatenated Fact data models, along with many other QlikView and Qlik Sense development techniques.