The provisions of Article 201 (Tax Withheld from Retirement Income) of the new Act, and Appended Table 8 of the new Act and the annexed table to that Table, apply to severance pay or other such compensation as prescribed in Article 199 (Obligation to Withhold Taxes from Retirement Income) of the new Act (hereinafter referred to as "severance pay or other such compensation") that is payable on or after January 1, 1973 and is paid on or after the effective date, and the provisions then in force continue to govern severance pay or other such compensation payable during that year that was paid before that date.