The period of time during which investors can commit to purchase shares of a security to be issued an initial public offering (IPO). In other words, investors can, during this period, buy shares of the new issue at the subscription price. The subscription period is preceded by a roadshow that can span two to three weeks. After the subscription period, it is no more possible for investors to subscribe.

In a different context, a subscription period for a rights issue is the period (one week or two) during which investors can exercise their rights and buy shares of the new issue at the subscription price (exercise price). Thereafter, the right to subscribe expires worthless. The expiration date of a subscription period is the last day on which the rights holder is allowed to exercise the right.