Waiver of interest: Board may reduce or waive interest where hardship, uncontrollable default, and taxpayer cooperation exist. The Board is empowered to reduce or waive interest under section 220 notwithstanding subsection (2), provided it is satisfied, on the Commissioner's recommendation, that payment would cause genuine hardship, the default arose from circumstances beyond the assessee's control, and the assessee has co-operated in inquiries relating to assessment or recovery proceedings.