If you've ever rented a house, you've probably noticed one thing that almost every rental agreement has in common — it lasts exactly 11 months. This isn't just out of common practice, rather it is shaped by legal provisions that treat rental agreements of up to 11 months differently from those that run for a year or more.Under Section 17 of the Registration Act, 1908, rental agreements exceeding one year must be registered, while registration remains optional for agreements of up to 11 months.