Scenario Branch

A scenario branch is a version of a plan with specific assumptions changed (best case, downturn, baseline), kept tied to the same underlying base case rather than copied out into a disconnected spreadsheet. The branch stores the changes, not a second copy of the whole model.

How branching differs from copying

A copied model duplicates everything: structure, definitions, historical actuals, and all the assumptions you did not intend to change. From that moment it diverges. Fix a mapping error in the base case and the copy keeps the error. Load a new month of actuals and the copy is comparing against a stale history.

A branch inherits the base case and overlays a small set of overrides. Structural fixes and new actuals flow through automatically. The branch stays a statement about assumptions rather than a snapshot of a model on a particular afternoon. This is what makes a what-if scenario survive contact with the next close.

Where branching gets difficult

Three problems come up. First, comparability: if two branches were created weeks apart against different base versions, the difference between them mixes assumption changes with base drift. Branches are comparable when they resolve against the same base version, so record that version explicitly.

Second, ownership. Branches multiply, and a branch nobody owns is a branch nobody retires. Give each one an owner, a question it exists to answer, and an expiry.

Third, promotion. At some point a branch becomes the plan. That transition should be a deliberate, recorded action with an approver, not an informal agreement that everyone now uses the downturn case. Without it, nobody can reconstruct later which version the board actually approved.

What good looks like

A well-run set of branches is small, typically a baseline plus an upside and a downside, each carrying an explicit list of the assumptions it overrides and the base version it sits on. Comparing them shows the delta on a few decision-relevant lines rather than a full side-by-side of every account.

Rexfin recomputes each scenario branch against the same governed definitions and cited actuals as the base case, so comparing scenarios means comparing like with like. Changes recompute deterministically, and role scoping controls who can create, edit, or promote a branch.