Key legal question
Whether the taxpayer fulfilled the duty to cooperate in the 2004 tax assessment.
Extracted holding
No; the taxpayer did not provide the required substantiation for the disappearance of assets.
Extracted reasoning
The duty to cooperate includes producing books, vouchers, and other documents. Mere assertions about lifestyle or spending were insufficient, and the taxpayer failed to prove the use of CHF 111,000 withdrawn in cash.