In his 1922 book Socialism, Mises argued that in the stationary state of equilibrium there would be no problem of economic calculation. This theme is repeated again in Human Action. But assuming this establishes the theoretical possibility of economic calculation under socialism commits two fundamental errors: (1) misplaced concreteness, and (2) disregard for the social institutions that are required for economic calculation.
Hayek famously argued in "The Use of Knowledge in Society" that equilibrium models had misled economists in their analysis of socialism, and that they had confused the problem of imputation within planning, with the logical structure of a general competitive equilibrium state of affairs. But Ludwig von Mises had actually made this argument in Socialism some 20+ years earlier.
As Mises said: "under stationary conditions there no longer exists a problem of economic calculation to solve. The essential function of economic calculation has by hypothesis already been performed. There is no need for an apparatus of calculation. ... the problem of economic calculation is of economic dynamics, it is no problem of economic statics." See 1922, 120-121.
In Human Action (1949) Mises argued that: "The use of imaginary constructions to which nothing corresponds in reality is an indispensable tool of thinking. ... But one of the most important problems of science is to avoid the fallacies which ill-considered employment of such constructions can entail." (201-202).
We cannot do economics without equilibrium models as aids to thought, but we also have to guard against the ill-considered application of the equilibrium model. Fritz Machlup referred to this as "misplaced concreteness". Clearly, Lange, Lerner, Schumpeter, Samuelson, Bergson, et al, committed this error during the socialist calculation debate, and it was repeatedly made in textbooks for at least two generations. But even after Lavoie's Rivalry and Central Planning (Cambridge, 1985) had set the record straight, the problem of misplaced concreteness would creep back into the mindset of economists who argued that socialist economic calculation was possible just impractical. And this misplaced concreteness results in a failure to adequately account for the institutional context within which economic forces are at work.
Read Mises carefully --- not only did he get there first, but his analysis on these issues ran far ahead of those in his lifetime, and continues to outdistance that of friend and foe to this day.