When do our EB-5 investor clients start paying tax to the US?

You correctly state that there are six main stages to the EB-5 application process. I would also add the citizenship stage which would make these seven or eight stages, due to filing for, and approval of US citizenship status respectively. The first stage is the filing of, and the second stage is the approval of, the I-526 petition. Once the I-526 is approved, if their priority date is current, the fourth stage is applying for the conditional green card, either through adjustment of status through filing of I-485 if they are in the U.S., or through arranging of a consular interview if they are abroad. The fourth stage is the acquisition of the conditional green card. The tax obligations to the U.S. of your EB5 investor clients for global income start at the moment they obtain their conditional green card, and not at the moment of the filing, or approval of their I-526. That said, if they ever have U.S. income, no matter what kind of visa they are on, they would always have a tax liability on that portion of their income to the U.S. even before they file their I-526 application. One other thing they need to be cognizant is that if they have a low historical base on securities or real estate they purchased before obtaining their conditional green card, once they become a conditional green card holder, that historical tax base is used for capital gains purposes, even if the date is a very long time ago. Their tax obligations do not change at all in any of the other stages such as I-829 filing, or I-829 approval. The same is true for the citizenship stage. Once they complete 5 years, as of their initial acquisition of the conditional green card, they are eligible to apply and obtain US citizenship. All other things constant, since their tax obligations as a US citizen is identical to that of a green card holder, this does not alter their tax obligations either.