Publishing is Not the Same as Recording
First, make sure everyone understands what's being split. Publishing rights relate to the underlying composition — melody and lyrics. Recording rights relate to the master recording. These are two separate income streams that can be split differently. Many band disputes happen because people confuse the two.
The Equal Split Argument
Many successful bands (The Beatles, U2, Radiohead) use equal splits regardless of who wrote what. The reasoning: the song written by one person would sound entirely different — and be worth far less — without the band performing it, arranging it, and building an audience for it. Equality keeps peace and keeps bands together.
The Contribution-Based Argument
Other bands split by actual writing contribution. If one person genuinely writes 80% of the material, an equal split may feel unfair to them long-term and breeds resentment. If you go this route, document contributions per song in writing from day one.
The Hybrid Solution
Many bands use a hybrid: a base equal split, with a small writer's credit on top for whoever brought the original idea. For example: all members get 20% base, and the primary songwriter gets an additional 20% writer's credit from the overall pool. Agree on this framework before you have a hit — negotiating it after is much harder.