Post updated with corrections from the following posts.
Brokers with Qualified Intermediary status:
- Interactive Brokers
- Charles Schwab
- Swissquote
Brokers without Qualified Intermediary status:
- CornerTrader (?)
- Degiro (?)
Withholding tax for US-based securities:
- Domicile without US treaty, broker without QI: US takes 30%, non reclaimable
- Domicile without US treaty, broker with QI: US takes 15%, broker takes 15% and sends it to US
- Domicile with US treaty, broker without QI: US takes 30%, reclaim 15% locally and 15% from US
- Domicile with US treaty, broker with QI: US takes 15%, reclaim 15% locally
- Domicile with US treaty, Swiss broker with QI: US takes 15%, broker takes 15%, reclaim 30% locally