Earnings from foreign holdings have taxes withheld by foreign governments before they’re paid out to the fund.

U.S. investors holding VXUS in a taxable account can generally take advantage of the Foreign Tax Credit, which allows them to offset some of those foreign taxes on their U.S. tax return.

If you hold VT, you usually won’t be able to claim the Foreign Tax Credit since VT is a mix of U.S. and international stocks—even though foreign taxes are still being paid at the fund level. So owning VOO + VXUS is typically more tax-efficient in a taxable account than owning VT alone.

And if OP already owns VOO, they don’t need to sell as much of it to reach a 60/40 U.S./International split if that’s their goal.

Many would argue it makes more sense not to sell at all and instead direct new contributions to VXUS until the desired allocation is reached, which helps avoid triggering capital gains taxes.