In this paper, we introduce and study the notions of τ q -flat modules and τ q -coheret rings. First, by investigating the Nagata rings of τ q -torsion theory, we show that the small finitistic dimensions of T(R[x]) are all equal to 0 for any ring R. Then, we introduce the notion of τ q -VN regular rings (i.e. over which all modules are τ q -flat), and show that a ring R is a τ q -VN regular ring if and only if T(R[x]) is a von Neumann regular ring. Finally, we obtain the Chase theorem for τ q -coheret rings: a ring R is τ q -coherent if and only if any direct product of R is τ q -flat if and only if any direct product of flat R-modules is τ q -flat. Some examples are provided to compare with the known conceptions.