The following is a quote from IRS Instructions for form 1041:
Two or more trusts are treated as one trust if the trusts have substantially the same grantor(s) and substantially the same primary beneficiary(ies) and a principal purpose of such trusts is avoidance of tax. This provision applies only to that portion of the trust that is attributable to contributions to corpus made after March 1, 1984.
Now if two irrevocable trusts have the same grantor and the same primary beneficiary but a different number of trustees (One trust has asset protection, one does not.) are they considered substantially identical for income tax purposes?