In global PDF analyses, parton distribution functions (PDFs) are parametrised at a fixed input scale $Q_0$ and evolved to higher scales using the DGLAP equations. Since QCD evolution is fully determined within perturbation theory, the fitted PDFs should, in principle, be independent of the arbitrary choice of $Q_0$. In this work, we test this within the NNPDF framework by performing a series of fits at different starting scales, namely $Q_0 \in \{1.0,1.25,1.5,1.65\}$ GeV. We find that the resulting PDFs are consistent within uncertainties and the fit quality remains stable across this range, therefore confirming the invariance of PDF determinations with respect to the choice of starting scale.