  Radiative and Auger decay data have been calculated for modelling the K lines
in ions of the nickel isonuclear sequence, from Ni$^+$ up to Ni$^{27+}$. Level
energies, transition wavelengths, radiative transition probabilities, and
radiative and Auger widths have been determined using Cowan's Hartree--Fock
with Relativistic corrections (HFR) method. Auger widths for the third-row ions
(Ni$^+$--Ni$^{10+}$) have been computed using single-configuration average
(SCA) compact formulae. Results are compared with data sets computed with the
AUTOSTRUCTURE and MCDF atomic structure codes and with available experimental
and theoretical values, mainly in highly ionized ions and in the solid state.
