For a generic conformal field theory (CFT) in four dimensions, the scale anomaly dictates that the universal part of entanglement entropy across a sphere (Cuniv(S 2 )) is positive. Based on this fact, we explore the consequences of assuming positive sign for Cuniv(S 2 ) in a four dimensional scale invariant theory (SFT). In absence of a dimension two scalar operator O2 in the spectrum of a SFT, we show that this assumption suggests that SFT is a CFT. In presence of O2, we show that this assumption can fix the coefficient of the nonlinear coupling term d 4 x √ gRO2 to a conformal value.PACS numbers: 11.25.TqThe asymptotic structure of Poincaré invariant unitary quantum field theories in deep UV and IR is of great importance in physics. A deep understanding of this issue is achievable via the profound idea of Wilson [1]. According to this idea, the fixed points of renormalization group (RG) are dwellings of that asymptotics and therefore the asymptotic theories are scale invariant. Other new dwellings are the renormalization group limit cycles which also describe the scale invariant field theories. Remarkably, with a few known exceptions, unitary SFT's always exhibit full conformal symmetry. A natural question is whether it is possible for a theory to be scale invariant but not conformal invariant? The converse question, i.e., whether a theory can be invariant under conformal transformations but not under scaling, is easy to answer. The commutator between the conserved generators of translations and conformal transformations gives the scaling generator together with the Lorentz ones. This means that Poincaré plus conformal invariance comprises scale invariance. The converse is still an open question since Poincaré and scaling generators form a closed algebra.Recently there were considerable efforts to answer this question and the task has been done in some spacetime dimensions, but the problem is still open for D = 4. Although some comprehensive arguments are available in 4D, they still suffer from serious loophole. In this paper we study the problem of scale vs conformal invariance in 4D by making use of entanglement entropy. For a generic CFT in 4D, the scale anomaly dictates that the universal part of entanglement entropy across a sphere (C univ (S 2 )) is positive [2]. Based on this fact, we explore the consequences of assuming positive sign for C univ (S 2 ) in a 4D SFT. In absence of a dimension two scalar operator O 2 in the spectrum of a SFT, we show that this assumption suggests that the SFT actually is a CFT. In presence of O 2 , which is actually related to the loophole in previous studies, we show that this assumption fixes the coefficient of the nonlinear coupling term d 4 x √ gRO 2 to a conformal value.The paper is organized as follows. The first section is devoted to a comprehensive review on previous studies on the subject of scale vs conformal invariance by emphasizing on 4D. Since our work is highly based on using scale anomaly in SFTs we will dedicate some parts of the first section to this topi...