I'm interested in investing in the SPDR S&P 500 ETF. How would the US tax me for this?

The 30% tax is on the dividends. So if your dividends you get every year is $100, US government will take $30 and you get $70. There are no capital gain tax for Singaporeans investing in US stocks. So if your ETF price grow from $10 become $20, its all yours. You either sell your stocks or use dividends to pay for your retirement.

There is no retirement tax.

There is also 40% estate tax in US. So if you die with 1 million in the ETF, 400k goes to US government and 600k goes to your family.

Books ask you to sell 4% every year of your total stocks/etfs to pay for your retirement. Because stocks typically goes up in the long run. But its better to reduce it further to around 3%-3.5% to be safe. So if you need 100k every year for your retirement, you would need to have 2.5 million in the ETF for the 4% to work and 3.3 million for 3% to work.

Alternatively, you can look at VUSD ireland domiciled ETF for S&P 500 which will reduce the 30% dividends tax to 15% and theres no estate tax.

Singaporeans does not have capital gain tax and estate tax in Singapore. So only the other countries taxes matters when you invest overseas stocks.​​​

You can take a look at this article: https://taxsummaries.pwc.com/ID/United-States-C...