I know you said you had no other debts but sharing for others: if you have significant other debts you are claiming interest tax relief on then your DA-1 may be rejected.
Was the case for me when I was claiming ~CHF3k in interest on student loans off my taxes and also trying to claim ~CHF500 in DA-1 refunds.
I’m still not sure if this is really a valid reason. Is there any law for this?
Refund for US WHT is based on a double taxation agreement. You’re entitled only to the amount that avoids double taxation. This means that your refund is capped not only by the US WHT amount but also by the amount of Swiss taxes. And for this purpose, only the part of Swiss income taxes related to income from these US ETFs is considered.
The tax rate used for this calculation is the effective/average tax rate, not the marginal tax rate. The gross dividends are reduced by deductions related to assets (e.g. management costs) and liabilities (e.g. deductible interest). This reduction is applied proportionally (percentage of US ETFs of total assets). This makes sense as these deductions reduce your Swiss income taxes and thus, they don’t qualify for double taxation relief.
reduction = related tax deductions x tax value of US ETFs : tax value of all assets
maximum refund = (gross dividends - reduction) x tax rate
If the maximum refund is greater than or equal to 15% of gross dividends, you get a refund for the whole US WHT. If it’s lower, you only get that part. If it’s below CHF 100 you don’t get anything.
Note that Switzerland doesn’t get this money back from the US. Switzerland waives these taxes as required by the DTA. That makes it clear why it would never make sense to refund more than what’s taxed in Switzerland.
Details (in German):