The basis for an allowance of contribution to a joint tenancy by a surviving joint tenant is the claim therefor by the survivor in completing the inquiry on form IT-22, Inheritance Tax Declaration.

Contribution claims are required to be traced back to their remote origin to prove that the original source of the funds contributed by the survivor was not the decedent. Thus, if a father gave money to his son and some years later the son used this money to create a joint tenancy with the father, the entire joint tenancy would be taxed at the father's death since the father was the contributor of the funds when they are traced back to their remote origin.

The contribution allowable to a surviving joint tenant must be reduced by its proper proportion of certain of he deductions applicable to the joint tenancy. Some of the allowable deductions under the Inheritance Tax Law apply as a proportionate reduction of the entire joint tenancy. Others apply only to the decedent's share of the joint tenancy.