If I skip (unintentionally) sehri of nafl fast, will the fasting be valid?

Answered according to Hanafi Fiqh by Darulifta-Deoband.org

بسم الله الرحمن الرحيم

(Fatwa: 249/203/B=02/1435)

Yes, your sawm (fast) will be perfectly valid. It is mustahab practice to get up before Fajr time and to have sehri, it is not wajib or fardh which if missed may affect the validity of sawm.

Allah knows Best!

Darul Ifta,
Darul Uloom Deoband