In Jain tradition, chanting of navkar mantra / prayer is generally allowed during menstruation, because chanting is a mental and verbal practice and does not involve harm.

However, some families or temples may follow stricter customs and may avoid certain puja, temple entry, or ritual activities during periods. This is based on tradition, not on the core spiritual value of chanting itself.

So, in simple terms:

• Chanting is usually allowed
• Physical rituals may be restricted in some traditions
• Keep the practice pure, respectful, and peaceful

If you want, I can also explain this according to Digambar or Shwetambar tradition.