Dimensions & cost centers

A shop wants to know COGS by location, spend by department, revenue by customer, without carving a separate account for every combination. A reporting dimension is how Carbon does that: a company-defined tag axis that gets attached to individual journal lines, so the same handful of accounts can be sliced along whatever axes the business reports on. Cost centers are one such axis, plus a standalone hierarchy for organizing cost ownership.

Dimensions and cost centers live in the accounting module and are defined once per company group, alongside the chart of accounts.

What a dimension is

A dimension is a named tag axis with an entity type that decides where its values come from. You define it once (dimension table, name + entityType, scoped by companyGroupId); every posted journal line can then carry at most one value on that axis.

The full set of entity types (dimensionEntityType, accounting.models.ts:577): CostCenter, Custom, Customer, CustomerType, Department, Employee, FixedAssetClass, Item, ItemPostingGroup, Location, Process, Supplier, SupplierType, WorkCenter. Each was added to the database enum as the posting paths learned to resolve it.

A dimension carries two flags: active (an inactive dimension stops being attached to new postings) and required. Names are unique per company group.

How a value lands on a journal line

Dimensions are stored in a join table, journalLineDimension, with one row per tag: journalLineId, dimensionId, and a valueId. That valueId is deliberately polymorphic — for a Custom dimension it points at a dimensionValue.id; for an entity-type dimension it points straight at the entity row's id (location.id, customer.id, costCenter.id). It is intentionally not a foreign key; the reference target depends on the dimension's entity type and is enforced in application code (20260228024512_dimensions.sql:131). A line can hold at most one value per dimension (UNIQUE("journalLineId", "dimensionId")).

The interesting part is that you rarely set these by hand. When accounting is enabled and a document posts, the posting path resolves them automatically:

1. It loads every active dimension for the company group into a map keyed by entity type (post-shipment/index.ts:171).
2. As it builds each journal line, it already knows the source facts — the customer, the item, the item posting group, the location, the cost center behind that line.
3. For each of those facts, if an active dimension exists for that entity type, it attaches a journalLineDimension row pointing the valueId at that entity's id (post-shipment/index.ts:1222). No dimension defined for an axis means no tag on that axis — defining the dimension is what turns tagging on.

So a Location dimension isn't a field you fill in on the shipment. You define the dimension once, and from then on every shipment, receipt, invoice, and inventory posting carries its location automatically, because the posting already knew the location. The same pattern runs in post-receipt, post-sales-invoice, post-purchase-invoice, post-inventory-adjustment, post-payment, and the other posting functions.

Cost centers

A cost center is a named organizational unit for grouping cost — a plant, a line, a service team. Cost centers form a hierarchy: each one may name a parentCostCenterId, so you can roll child centers up into a parent (getCostCentersTree, accounting.service.ts:2212). Each carries an owner (ownerId, a user) responsible for it.

Cost centers play two roles:

• A standalone tree (costCenter table, scoped by companyId) you assign to purchase lines and other records to attribute spend to the responsible unit.
• A dimension axis. Define a dimension with entityType: "CostCenter" and postings begin tagging their journal lines with the cost center the source document carries — exactly like any other entity-type dimension. That's how cost-center-level P&L reporting works: the cost center is a tag on the line, resolved from the document at posting time.

There is no costCenterId column on journalLine itself. A cost center reaches the ledger the same way every other axis does — as a journalLineDimension row whose valueId is the costCenter.id.

Using dimensions in reports

Dimensions exist to be sliced. Because the tag lives on the individual journal line, any report built from journal lines can group or filter by a dimension value: COGS by location, expense by department, revenue by customer. The chart of accounts stays small — you don't create COGS – West and COGS – East accounts, you post to one COGS account and slice it by the Location dimension.

Because dimension slicing reads posted journal lines, it's only meaningful once a period's postings are final. See period close for how a month's balances get snapshotted.

Related