The peroxymonosulphate anion, ${\mathrm{HSO}}_5^{-}$, has :

The peroxymonosulphate anion, ${\mathrm{HSO}}_5^{-}$, has four Sulphur-oxygen bonds and one oxygen-oxygen bond

Since there is just one link between these oxygen atoms, they will each have six valence electrons and a shared valence electron with Sulphur.

These oxygen atoms desire an additional electron to completely occupy their outermost shell. The oxygen atom will get an electron and receive a net -1 charge as a result.

The peroxymonosulphate anion, ${\mathrm{HSO}}_5^{-}$, has four sulphur-oxygen bonds and one oxygen-oxygen bond