1.12.1 Calculation errors

In T 13/83 (OJ 1984, 428), a case decided prior to G 3/89 (OJ 1993, 117) and G 11/91 (OJ 1993, 125) (see chapter II.E.4. "Correction of errors in the description, claims and drawings – Rule 139 EPC" below), the board held that a correction of an erroneous technical calculation was allowable under Art. 123(2) EPC 1973 if the amendment would be regarded by the skilled reader as clearly implied by the disclosure of the application as filed. If more than one arithmetical possibility of correction could be envisaged, the correction chosen had to be the one which the application as a whole clearly implied (see also T 784/96, which cites T 13/83). See also T 1242/07 in which the board found that the correction of an obvious calculation error satisfied the requirements of Art. 123(2) EPC.