For a make-to-order manufacturing system, the uncertainty and flexibility of the due dates required by customers and the production capacity owned by the manufacturer can be modeled in a fuzzy environment. In this paper, a combined due-date assignment and production planning methodology for the make-to-order manufacturing systems is developed. The fuzzy approach determines the optimal due dates for the manufacturer based upon a "rough-cut" resource balance, while a customer can request earlier due dates by paying a higher price to cover the extra manufacturing cost incurred. The resulting fuzzy due-date bargainer is exercised using manufacturing resource planning (MRPII) data from a furniture manufacturing company. Experimental results indicate its potential as a useful tool for real applications.