“Authorized agent or officer”, as used in this chapter, includes any trustee, mortgagee or receiver in possession of or operating any such railroad in the state, and “net railway operating income” means railway operating revenues less railway operating expenses, railway tax accruals and uncollectible railway revenue, including in the computation thereof debits and credits arising from equipment rents and joint facility rents. Each such corporation, on or before the first day of July in each year, shall make a return to the Commissioner of Revenue Services, in such form as the commissioner may prescribe and signed by its treasurer or an authorized agent or officer, specifying: (1) The name of each railroad operated by such corporation during the year ended the thirty-first day of December next preceding; (2) the number of miles of all railroad tracks, including yard tracks, sidings, branches and spurs, which were operated by such corporation at any time during the year ended said thirty-first day of December, and the number of miles within this state of all such railroad tracks, including yard tracks, sidings, branches and spurs so operated; (3) the amount of gross earnings of such corporation from all sources from its operation, and the amount of net railway operating income of such railroad during the year ended said thirty-first day of December, or the portion of such year that such corporation has carried on business in this state; and (4) the assessed value of all real estate in this state assessed in the name of such corporation, or of a corporation all of whose property is operated by it, with a specific list of the same and the amount of taxes paid upon any such real estate in any town, in the year ended said thirty-first day of December.