The Internal Revenue Service is going after the estate of Bill Davidson, former owner of the Detroit Pistons and auto industry supplier Guardian Industries, to the tune of more than $2 billion.

In a filing made public in Tax Court on Wednesday, the IRS disputed the estate representatives’ assertions, filed in June, that the estate tax was grossly inflated, according to the Detroit Free Press.

Among the objections that the IRS has with the estate are the valuation Davidson’s accountants placed on stock in his company, for purposes of gifts, trusts and other transfers to family members.

One of the techniques used was Self-Canceling Installment Notes, or SCINs, in which Davidson sold assets with the proviso that the payments would be canceled when he died. The IRS said he didn’t properly calculate his own life expectancy, with the result that family member payments amounted to less than fair market value.