In Jainism there is no universal ban on cutting hair on Ashtami (the eighth lunar day). Hair cutting is generally a normal activity for household (laity) followers. The only clear exception is for monks/nuns: those who have renounced worldly life (e.g., after taking Diksha) traditionally keep their hair shaved as part of their renunciation, and they do not cut hair again.

So, for a layperson, cutting hair on Ashtami is normally permitted. If you’re following a specific vow or local guidance from your guru or community, follow that guidance.