Scenario Source Periods let you seed a new Budget, Forecast, or Dependent scenario with data copied from an existing scenario — period by period — so you start from a realistic baseline instead of a blank slate. This guide explains what source periods are, how to assign them, what the Fixed column does, and the single most important thing to understand: the copy is a one-time capture, not a live link. For the broader picture of scenario types and management, see Scenarios in Catalyst.
What Are Scenario Source Periods?
When you create a new Budget, Forecast, or Dependent scenario, a Source Periods section expands at the bottom of the creation form. It lets you initialize the new scenario with data from an existing scenario, choosing the source separately for each period.
This is what saves you from building every budget or forecast from scratch. Instead of typing values into all twelve periods, you point each period at a scenario that already holds sensible numbers — then refine from there in Planning.
Optional, not required. If you plan to populate every period yourself, you can skip source periods entirely and start blank. Use them when an existing scenario gives you a useful head start.
When the Section Appears
The Source Periods section only expands for scenario types that hold planned data you'd want to pre-fill. You'll see it on:
Assigning a Source to Each Period
Inside the Source Periods section, each period has its own source selector. A typical setup pulls recent closed months from Actuals and the remaining months from a budget or forecast.
Open a Budget, Forecast, or Dependent scenario form
Go to Administration → Scenario under Site Management and start a new scenario of one of these types. The Source Periods section appears at the bottom.
Choose a source scenario per period
For each period, select the scenario whose data should seed it. Leave a period unset to enter its values manually after creation.
Decide whether to mark periods as Fixed
Use the Fixed column to control how profitability is calculated for that period (explained in the next section).
Save the scenario
Catalyst captures the source data once at this moment. The copied values now belong to the new scenario and can be edited freely in Planning.
The "Fixed" Column
Alongside each period's source selector is a Fixed checkbox. It changes how profitability data is calculated for that period when the source data is captured.
When to use Fixed. Choose Fixed when you want the captured profitability to reflect a precise end result rather than be recalculated from percentage rates — useful for closed or finalized periods where the numbers should not shift.
The One-Time Capture (Read This First)
This is the part that trips people up, so it's worth being precise about. When you save a scenario with source periods, Catalyst takes a one-time snapshot of the source data at that moment. It does not establish an ongoing connection.
In practice, that means if you later edit the source scenario, those edits will not appear in the scenario you built from it. The two are independent the instant the new scenario is created.
The golden rule. Finalize the source scenario before you create the new scenario. Whatever the source contains at creation time is exactly — and only — what gets captured.
If You've Already Created the Scenario
Suppose you created a budget or forecast from a source scenario, then realized the source still needed changes — and now those changes aren't showing up. That's expected behavior, not a bug. Because the capture already happened, the fix is to re-seed from an updated source. Here's the recovery sequence:
Delete or archive the scenario that's out of date
Since the captured data won't update on its own, remove the new scenario that's missing your changes. Archive it instead of deleting if you want to keep a record.
Update the source scenario
Make every change you need in the source first, so its data is fully current and aligned with what you want copied.
Recreate the scenario from the updated source
Create the scenario again, selecting the now-updated source. The fresh capture will include your latest changes.
When You Actually Want a Live Link
Source periods are the right tool when you want a one-time head start. If instead you need a scenario that continuously reflects another, you want a different feature. Here's how to tell them apart:
Want a scenario that stays in sync automatically? Learn how Dependent scenarios and Actuals Thru work together.
🎓 Knowledge Check
Test your understanding of scenario source periods
1. You update a source scenario after creating a budget from it. What happens to the budget?
Related Resources
Scenario Source Periods give you a fast, realistic starting point for new budgets and forecasts by copying data from an existing scenario, period by period. Just remember the one rule that governs everything: the copy is a one-time capture taken at creation, not a live link. Finalize your source first, use the Fixed column when you need locked-in profitability figures, and reach for a Dependent scenario or Actuals Thru when you need ongoing synchronization instead.
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