I would love to get recommendations on favorite shopping spots 8n Madrid. Hoping to support Spanish business while we are visiting. Thank you!

sorry, not a clue what ISO are, anyone any ideas?

ISO=in search of??

Anyway, the Salamanca District has the nicest shops, and some great restaurants. In my fairly limited experience of Madrid..

I assume In Search of. Either that or International Standards Organization. But I'm fairly sure the OP meant the first one

Not a term I'd come across but thanks for illuminating.

Yes, in search of - thank you!

Yes, Salamanca has all the upscale shops .
There are also many shops near Sol.

Don’t know what you might be shopping for, but if you have any interest in or need for art supplies, or need a gift for someone who does, art stores in Spain are great and there are several in Madrid. I can’t make a specific REC because I do not remember which ones I shopped at, but I bought a ton of things. No savings really, but such fun to see more traditional looking shops with beautiful pastels, brushes, etc.

Gifts. Real Fábrica at Calle Cervantes 9, nearby Plaza Santa Ana https://realfabrica.com/en
Candy. La Violeta at Plaza de Canalejas, nearby Puerta del Sol https://www.lavioletaonline.es/en/
Hand-made bags. Ollomao at Calle de la Fe 18, Lavapies https://ollomao-taller.negocio.site/
Antigua Casa Crespo at Calle Divino Pastor 29 https://www.antiguacasacrespo.com/en/
Esparto grass. Espartería Juan Sánchez at Calle Mediodia Grande 3, La Latina https://www.esparteria.com/
Glove shop https://www.esmadrid.com/en/shopping/guantes-luque
Ceramics. Amasarte at Calle de las Minas 6, Malasaña https://www.amasarte.es/#tienda
Jewelry. Uno de 50 at Calle Fuencarral 17, near Gran Vía https://www.unode50.com/es/en/

For ceramics, this place near metro Santo Domingo

https://www.antiguacasatalavera.com/

It really depends what you are looking for and why. I think you will know Spanish brands/shops. Zara is Spanish. Bimba y Lola is expensive brand for accessories. Loewe expensive brand for handbags. Mango, Tous. Suarez and Desigual are other well-known Spanish brands.