Subscription period rules require minimum and maximum open dates, with mandatory extension on price revisions and limited force majeure extensions. A public issue of debt securities and non-convertible redeemable preference shares must be kept open for subscription for a minimum of two working days and a maximum of ten working days. Revision of the price band or yield requires the issuer to extend the disclosed bidding period by at least one working day, and in force majeure or similar events the issuer may extend the bidding period for reasons recorded in writing, provided the overall bidding period does not exceed the prescribed maximum.