In the present work, we have computationally studied mono-substituted Keggin, [M(H2O)PW11O39] q-, and Wells-Dawson, [M(H2O)P2W17O61] q-, which have previously been experimentally synthesized. By employing DFT calculations, we have calculated the standard reduction potentials for the pH-independent redox processes present in Keggin [M(H2O)PW11O39] q-(M = Mn(III/II), Fe(III/II), Co(III/II), and Ru(III/II)) anions. Best practise for reproducing experiment redox potentials is not consistent for every anion tested in this work. For Fe(III/II) and Co(III/II) by selecting B3LYP / TZP methodology, the error in calculation can be reduced to 0.01 and 0.10 V, respectively. Mn(III/II) and Ru(III/II) were best fitted with B3LYP*/TZP and PBE / TZP methodologies, respectively. The employment of hybrid, and long-range-corrected GGA (LC-GGA) functionals did not improve the reproduction of experimental crystallographic structures. The description of the terminal metal-oxygen bonding remains a shortcoming of all methodologies tested here. This computational work provides a basis for computing redox potentials of mono-substituted-polyoxotungstates that can be compared, to a certain extent, to experimental potentials. Notable error in these calculations remain and it is imperative that the computational approach is further optimised. Future work will go into exploring the influence of counter-cations used for charge neutralization in [M(H2O)PW11O39] q-. ASSOCIATED CONTENT Supporting Information. The supporting information detailing computational information is available, see SI document.