The appearance of spurious transitions to the continuum can be avoided in TDKS simulations via ad hoc replacement of positive SCF eigenvalues (representing unbound states) with complex-valued eigenvalues in the MO representation of P(t). This transformation has the effect of giving those states a finite lifetime that can be made arbitrarily short by selecting the imaginary part of the eigenvalue. An alternative approach would be to introduce a complex absorbing potential. However, both methods have some arbitrary parameters that must be adjusted, potentially on a case-by-case basis, and we have not pursued either method in this work. Instead, we turn to dipole filtering as a diagnostic to understand the origins of various features in a given TDKS spectrum. presents TDKS spectra for methionine, using the SRC1-r1 functional in four different basis sets, in the region from 500-550 eV. LR-TDDFT/CVS calculations suggest that the O(1s) → LUMO transition should be found at ≈ 532 eV for this functional and these basis sets, but the TDKS spectra have pronounced features at lower excitation energies. The oxygen K-edge spectrum can be extracted from the TDKS results by filtering on the O(1s) orbitals. In a small basis set such as 6-31+G(d), this has virtually no effect on the spectrum within the indicated energy range (Fig. ), and the first peak that is observed is in fact the O(1s) → LUMO transition, at 531.9 eV. As such, the issue of pre-edge artifacts in TDKS spectra may go unnoticed if low-quality basis sets are used. With the benefit of hindsight, one can just barely make out two very small pre-edge features at 520.6 and 527.4 eV in the SRC1-r1/6-31+G(d) spectrum, although these might : TDKS absorption spectra for methionine computed using the SRC1-r1 functional in various basis sets. All simulations used Padé approximants with tmax = 600 a.u. and ∆t = 0.02 a.u., following a δ-function impulse with Ēx = Ēy = Ēz = 10 -4 a.u.. Spectra labeled as "full" are based on the complete dipole moment function whereas those labeled "O(1s)" exclude all contributions to D λ (t) except for those originating with the two O(1s) orbitals. The O(1s) spectrum in (a) has been shifted to better reveal the baseline in both spectra, and the arrows highlight two very small pre-edge features.