29- Various items which in the previous law were included under Schedule VIII, such as the rental of commercial enterprises, royalties from invention patents and trade marks and rental of tangible personal property, are considered as commercial activities for purposes of the new law, and income derived therefrom, although received by individuals, is subject to the tax on combined income of enterprises. 45. Payment of the tax; The manner and due date for the payment of the tax also depend on the nature of the income. The tax must be withheld by the payor and remitted to the corresponding Federal Collector's Office during the following month, in the following cases indicated in preceding point 44. Dividends (a-l); participation of profits paid to debenture-holders or others (a-7); excess on liquidation of companies or redemp-tion of capital stock (a-8); interest on bonds, debentures, etc. (c-2); interest received from national credit institutions (c-3) and interest paid to foreigners for loans in the general interest (c-4). In all these cases, with the withholding and payment of the indicated tax, the tax responsibility of the recipient Is met. The tax is payable (1) by means of stamps attached to the documents relating to each amount received and (2) by means of a tax return covering income obtained during the calendar year, which is presented in the following month of April, in the following cases: Dividends paid by foreign enterprises (a-3); interest and other income from all types of acts, agreements, contracts or trans-actions not specifically mentioned (c-8); royalties for governmental concessions and for contracts relating to the exploitation of the subsoil (d-1 and d-2); income from transfer, contribution or rental of governmental concessions if machinery and equipment are not included (e-2); and bonding premiums paid to unauthorized Institutions (j). The provisional payment (in stamps) shall be 10% of each amount received or the amount which results from applying the tax rates of Exhibit B, whichever is higher. In the cases of rental (f) and sub-rental (g) of urban real estate, the payment is also made in stamps; this payment is not pro-visional but is definitive. The same procedure is applicable to interest received from foreign credit institutions (c-3). The payments are made in cash by the taxpayer himself, and on varying dates, in the following cases: Distributable profits of branches or agencies of foreign enterprises (b), during the three months following the close of the fiscal year; income from the transfer, contribution or rental of governmental concessions if machinery and equipment is included (e-l), during the following 15 days; sale of urban real estate (h), during the 30 days following the signing of the title deed, or during the 15 following days if the transaction is not recorded in a title deed.