The EPO makes corrections on request or of its own motion (T 150/89). In T 212/88 the board held that correction of errors under R. 89 EPC 1973 (R. 140 EPC) had to be done by means of a decision, with retrospective effect from the date of the original decision. In T 116/90 of 3 December 1990 date: 1990-12-03 it was held that it was unnecessary to re-date the decision as from the date of correction.
In T 130/07, the board reiterated that a correction made no difference to either the date of the corrected decision or the appeal period triggered by its service (as previously held in T 212/88 and T 1176/00). It nevertheless reprimanded the EPO for its continued failure, despite the case law already established on the point, to avoid issuing such "second decisions" bearing a seemingly new date and so seemingly triggering a fresh appeal period and instead issue properly reasoned correction decisions clearly marked as such (similarly T 105/11). On the issue of the distinction from genuine second decisions, see III.A.2.6.
In T 105/11 the board held that in application of the principle of the protection of legitimate expectations, the statement of grounds of appeal was deemed to have been filed in time, even though the appellant directed the notice of appeal and the statement of grounds of appeal against the correction decision with an alleged new date.