The three-way decisions theory is formulated based on the notions of acceptance, rejection and noncommitment. The theory, which is an extension of the commonly used binary-decision model with an added third option, has been widely used in many fields and disciplines. Considering the costs of noncommitment are often the same with misjudgment in the positive region or negative region. That the basis of noncommitment decision converting to acceptance or rejection and the invert costs function are given as an aid in the scheme of decision making, further improved the three-way decisions.