Nepal to Vietnam: East Himalaya, India, Nepal, Tibet as per POWO;
Common name: Kisopa Magnolia • Garhwali: चाम Chaam • Kumaon: Chaur • Nepali: चोलसी Cholsi, बन चाँप Ban chanp

Deciduous trees, about 10-18 m tall. Bark gray, plain with thin lenticelled branchlets, glabrous, stipular scars are prominent on the branchlets, buds grey, sericeous. Leaves simple, alternate, ovate-elliptic, lanceolate-elliptic or oblong, 12-24 × 3-10 cm across, base abruptly cuneate or rarely rounded, margin entire, apex acute or shallow acuminate, thinly coriaceous, shining glabrous above, paler dull, glabrous beneath, turning yellow before falling, lateral veins 10-15 on either side of the midrib, slightly arched towards the outer margins, reticulate veinlets very close and fine, petiole pubescent, about 1.5-3 cm long, stipules oblong, about 1.5 cm long, pubescent with grey or rusty brownish hairs, stipular scars usually about 1-2.5 cm long. Flowers bisexual, solitary, appearing with the leaves, white or cream or pale yellow, pleasantly fragrant, about 3-5 cm across, buds about 1.2 cm across, Perianth parts about 12-15, obovate-oblong or oblanceolate, apex truncate, glabrous, 2-3 x 0.5-0.8 cm across, Sepals narrow-obovate, petals scarcely narrower than the sepals. Stamens numerous, shorter than the gynoecium, carpels silky hairy, styles recurved, Gynoecium obovoid or ellipsoid, Fruiting receptacle 3-5 x 2 cm across. Fruiting carpels elliptic-ovoid, sessile, compressed, rounded near the base, with beaks near at the apex, about 8-11 x 6-7 mm across, seeds 3-4, glossy red, obovoid

Subtropical forests at an altitude of about 1400-1800 m.
Local Distribution: Arunachal Pradesh, Assam, Meghalaya, Sikkim, Uttar Pradesh, West Bengal. Global Distribution: Asia: Bhutan, China, India, Nepal.
(Attributions- Ganeshaiah, K. N., UAS, Bangalore, India. Kailash, B. R., UAS & ATREE, Bangalore, India. Indian Bioresource Information Network (IBIN), Department of Biotechnology, New Delhi, India as per India Biodiversity Portal)

SK 2839 10 November 2020 : 8 very high resolution images.

Location: Kathmandu Valley
Date:  October 2020 
Elevation: 1350m.
Habitat  : Wild
Magnolia doltsopa (Buch.-Ham. ex DC.) Figlar ??
Syn : Michelia doltsopa Buch.-Ham. ex DC.

I think they look different from Magnolia doltsopa (Buch.-Ham. ex DC.) Figlar as per images and details herein.
Also could not find a match as per comparative images at Magnolia. Pl. check other species as listed at this page from Checklist of Nepal.

I have already checked efloranepal.