No—registration of a partnership firm under the Indian Partnership Act, 1932, is not legally mandatory. Two or more people can form a partnership and operate a business based on a partnership deed without formally registering with the Registrar of Firms. However, an unregistered firm faces significant practical limitations: The firm cannot file a lawsuit to enforce a contractual right against a third party — it can be sued, but cannot sue. Partners cannot sue each other to enforce rights arising from the partnership agreement. The firm cannot claim a set-off (counterclaim) in a legal proceeding.
Banks and financial institutions typically require a registered firm for opening a current account or applying for a business loan. Government contracts, tenders, and scheme applications (like PMEGP) generally require registration. In practice, registration costs very little (₹2,000-5,000 in most states) and takes 1-3 weeks—the protection it provides against legal disputes and the access it opens for banking and formal business relationships make it worth doing for any serious business.