Who is responsible for paying tax on the income from Kumail's irrevocable trust?

The correct answer lies in the nature of how irrevocable trusts are taxed. In the case of an irrevocable trust, the trust is considered a separate taxable entity. This means that the trust itself is responsible for paying taxes on any income it generates, rather than passing that obligation directly to the grantor (Kumail) or any other individuals, such as the beneficiaries or the trustee.

The trust's taxation is based on its own income, deductions, and credits. It files its own tax return (Form 1041) to report income earned within the trust. If the trust distributes income to its beneficiaries, then those beneficiaries may be taxed on that distributed income, but the trust itself remains the initial taxpayer on any undistributed income.

In this context, the other options do not hold because the grantor does not pay taxes on income generated by the trust after it has been irrevocably established, the bank acting as trustee simply administers the trust and has no tax responsibility, and the beneficiaries are only responsible for tax on income they actually receive from the trust distributions, not on the income the trust earns while it remains undistributed.