This is going to be very species-specific, what organism are you using?

The annotation in NCBI is a "best guess" unless its supported by other information. If the region of DNA hasn't been annotated, you could try comparing to related genes.

For plants, you can try the very "old-school" approach of just grabbing the 1000 or so bases upstream of the start site. But if there are exons you don't know about, long 5' UTR, etc that adds a lot of uncertainty.

Thank you for your response,

I'm working specifically on the human genome, and I'm trying to identify the promoter region of a particular gene using the DNA sequence available in NCBI. However, since I didn’t find clear promoter annotation, I was wondering if you could suggest the best approach for locating the promoter in the human genome.

Regard,

Reza