Cost Control
You know why creating a set locks the budget under it, what stays frozen versus what you keep working, and how a period's tracking actually continues.
A cost control set is always created **under one budget**. It does not hold a budget of its own — it holds what has actually happened against the budget it sits on.
This is the module's defining trade, and it is the first thing you will meet: create a set, then find the budget will no longer accept an edit. The Budgets Manager shows a padlock in its **Lock** column.
It is deliberate. Cost control's whole job is to compare reality against a plan, and a plan that can be edited afterwards is not a plan — it is a moving target that makes every variance meaningless. Locking the budget is what makes *Budget minus Forecast* a number worth reading.
The **Budget** column keeps reading the real, locked budget directly, which is why it cannot move once a set exists. Everything else in the set is still yours to work.
The set holds its own copy of every account's quantity, unit and price, identical to the budget's at the moment you created it. The **Recalculation** tab is where you keep adjusting that copy — the shoot gained two days, a rate was renegotiated — and the result lands in **Forecast**, never in Budget. See [recalculate an account](/kb/article/recalculate-an-account).
That is the actual shape of the trade: the figure you were approved against cannot be argued with in hindsight, but building the forecast that compares against it is still the daily work.
Budgets do change: a financier requires a restructure, a whole department is rescoped. The route is to **copy the budget** and work in the copy, leaving the locked original with its set intact as the record of what you were measuring against.
That is the accurate version of the change. The old set still says what you compared to and what happened; the new budget starts a new comparison.
| From the budget | Used for | | ------------------------ | --------------------------------------------------- | | The account structure | which rows the set can track | | Each account's total | the **Budget** column | | Companies, effects, tags | classifying cost items, and matching them on import | | Currencies | what a cost item can be entered in |
The **Budget** column is the locked figure — *approved baseline budget*, as the column says itself. Everything else in the set is yours.
A budget can carry more than one set. The ordinary way you get there is not by creating a fresh one from the budget again — that starts empty, with none of the cost items or forecast you have already built. It is by **copying** the set you already have, so a period's closing position survives before you carry on booking into the next one. See [copy a cost control set](/kb/article/copy-a-cost-control-set).
Copies do not interact. Each is its own tracking layer on the same locked budget, which is what makes last quarter's copy and this quarter's set comparable side by side. See [manage cost control sets](/kb/article/manage-cost-control-sets).
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