We believe that you should use the trust’s employer identification number (EIN) for the LLC account. The IRS’s Single Member Limited Liability Companies webpage states that a single-member LLC should use the owner’s social security number “for all information returns and reporting related to income tax.” (Note that if the LLC has to file employment tax or excise tax returns, it may need a separate EIN, but it would not be your institution’s responsibility to file those types of tax returns.) Because the trust is the sole owner of the LLC, it would be appropriate to use the trust’s EIN for the LLC’s account.

In this case, you have told us that the trust’s EIN is the grantor’s social security number (SSN). Because the trust is a revocable living trust, the IRS is likely treating it as a “grantor trust,” which file tax returns under the grantor’s SSN and aren’t required to obtain separate EINs. Form 1041 Instructions, Optional Filing Methods for Certain Grantor Type Trusts. With that in mind, it appears that you should use the trust grantor’s SSN on the LLC account.