JUDGMENT

G.N. RAY, J.

(1) LEAVE granted in all these five special leave petitions. Heard learned counsel for the parties and the appeals are disposed of by a common judgment in view of the fact that in all these matters common question of law and fact arise.

(2) M.R.F. Limited is the respondent in appeal arising out of Special Leave Petition No. 16265 of 1991. The said M.R.F. Limited (hereinafter referred to as the Company) is engaged in manufacturing automobile tubes, tread rubber etc. and the said Company entered into an agreement with the Kerala State Electricity Board (hereinafter referred to as the Board) for supply of electricity to the factory of the said Company. The agreement contained a provision for payment of power and energy supplied to the Company by the Board within 15 days from the date of the receipt of the invoice by the consumer, namely, the Company. It was further provided for in the agreement that in default of payment within the stipulated time, the payment was to be made with interest @ 18 per annum or at such other percentage as would be fixed by the Board from time to time.

(3) THE Board revised the tariffs for the electricity supplied by it in 1980, 1982 and 1984. The respondent-Company challenged such revisions by filing a writ petition before the Kerala High court being numbered as OP No. 2710 of 1985. Similar writ petitions were filed by other consumers challenging the upward revisions by the Board. All such writ petitions were heard along with the writ petition filed by the respondent-Company. The Kerala High court by common judgment dated 19-12-1985, struck down the revisions of tariff by the Board. The respondent-Company and other consumers were, therefore, entitled to the refund of excess amount on account of the payment of revised tariffs. The High court of Kerala directed that such amount paid in excess would be adjusted towards future bills to be issued by the Board.

(4) THE Board, thereafter, moved this court by filing special leave petitions inter alia challenging the correctness of the judgment of the Kerala High court dated 19-12-1985 striking down the revisions of tariffs. Such special leave petition was entertained by this court and an interim order was passed inter alia directing that pending disposal of the appeals before this court, there would be stay of the refund of charges already collected. It was further directed by this court that future charges would be collected to the extent of 50 only and the balance would be adjusted towards the past charges. The respondent-Company paid 50 of the demands for the months of March to June 1986 and adjusted 50 of the balance towards the refund due to them. Similar appeals were also preferred by the State Electricity Board against other consumers whose writ petitions were disposed of by the said common judgment by the Kerala High court. All the appeals preferred before this court were allowed by this court by judgment dated 26/8/1986 upholding the validity of revisions of tariffs by the Board.

(5) IN view of the said decision of this court dated 26/8/1986 upholding the tariff revisions by the Board, the respondent-Company and other consumers became liable to pay the amounts due on the basis of revisions of tariff including the amounts since adjusted by them in the manner indicated hereinbefore.

(6) THE Board thereafter raised a demand for payment of the amount by the respondent inclusive of interest @ 18 per annum. The respondent- Company did not challenge the liability to pay the excess amount in view of the revisions of tariffs but it refused to pay interest as demanded by the Board and such claim of interest by the Board was challenged before the Kerala High court by filing a writ petition numbered as OP No. 7686 of 1986. The learned Single bench disposed of the writ petition by holding that the demand for interest comprised in the demand notice (Ext. P-2 was not justified and the demand for