Subscription period rules for IDR offers require set open durations and allow extensions for price revisions and emergencies. Regulation 203 requires an initial public offer of IDRs to remain open for at least three working days and not more than ten working days. If the price band is revised in a book-built issue, the issuer must extend the disclosed bidding period for a minimum of three working days. In cases of force majeure, banking strike or similar unforeseen circumstances, the issuer may extend the disclosed bidding or issue period (book-built or fixed price respectively) for a minimum of one working day, with reasons to be recorded in writing, subject to the regulation's overall limits.