Attaching to a bill

Both the bill of materials detail page and the assembly BOM detail page (the definition for a subassembly) carry an Additional costs card on their Materials tab, below Components and Subassemblies. It’s where you say how much of a cost rate one finished unit consumes.

Attaching a cost rate

Open the detail page and go to the Materials tab.
Scroll to the Additional costs card and click Add in its heading row. A small dialog opens.
Pick a cost rate from the Add a cost rate… dropdown. Each option shows the cost rate’s rate and unit, and cost rates already attached to this bill are not listed.
Type the Qty / unit — the quantity consumed per one finished unit. It starts at 1.
Click Add.

Attaching takes effect immediately. The row appears, the card’s total moves, and every cost figure on the page re-computes.

What the row shows

Column	What it is
Name	The cost rate’s name from the catalogue.
Kind	A Labour or Overhead badge.
Quantity	Editable. What one finished unit consumes.
Unit · Rate	The cost rate’s unit and its rate, e.g. `hour · $40.00` — the two numbers the quantity is multiplied against.
Line cost	`quantity × rate`.

When at least one cost rate is attached, the card’s footer shows Additional costs per unit — the sum of every line cost, for one finished unit.

Changing a quantity later

Type over the number in the Quantity column. That edit is a draft, exactly like editing a material quantity on the same page: the figures on screen update as you type, but nothing is written until you Save the page. Leaving with unsaved changes prompts you first.

This is the one place attaching and editing behave differently. Adding and removing take effect straight away. A quantity change waits for Save, like every other edit on the Materials tab.

Removing a cost rate

One cost rate: open the ⋯ menu on its row and choose Remove cost rate. You’re asked to confirm, because the cost rate will no longer be part of this bill. Removal is immediate — there is no Save step for it.

Several at once: tick the rows you want, then use Remove in the bar that appears above the table. The confirmation names how many rows you’re about to remove, and warns you if any of them carry an unsaved quantity edit you’d lose.

A bulk removal can partly succeed. If it does, the card names exactly which rows failed, in a single banner, with actions to select just those rows or retry them. Nothing is reported as removed that wasn’t.

Either way, removing detaches the cost rate from this bill only — the cost rate stays in the catalogue and on every other bill that uses it.

The quantity is per one finished unit

This is the one thing worth getting right:

line cost = quantity × rate

The quantity is what one finished unit consumes, not what a batch consumes. If a candle takes one minute of a $40 / hour labour cost rate, the quantity is 0.0166667 — hours, because that’s the cost rate’s unit.

Quantities are fractional and stored exactly as typed. Don’t round 0.0166667 to 0.0167 to make it look tidy; on a run of 10,000 units that’s a real number of dollars.

If you have no cost rates yet

A cost rate has to exist in the catalogue before you can attach it. If your store has none, the card doesn’t show you an empty dropdown — it says No cost rates yet, explains that you create a labour or overhead rate in Settings first, and gives you a Go to cost rates button that takes you straight there. The Add dialog shows the same thing.

A card that’s simply empty on this bill reads differently: No additional costs yet — add labour or overhead to include it in the unit cost.

Attaching to many finished goods at once

To put the same cost rate on a whole batch of finished goods, do it from the list instead. Open Bill of materials in the app navigation — which opens the Finished goods page — tick the rows you want, then choose Cost → Add cost rates in the bulk action bar above the table.

Pick the cost rates. Choose one or more cost rates from your catalogue.
Say how much of each. For a hand-picked selection of up to 100 finished goods you get a grid — one quantity per cost rate per finished good — so you can vary the amounts. For anything larger, or when you’ve selected every row the current filters match, you set one quantity per cost rate that applies to all of them.
Apply. The dialog reports how many attachments were written and names any finished good it couldn’t write.

Reading it back in the Financial breakdown

On a bill of materials, the Overview tab carries a Financial breakdown card with three lines — Materials, Subassemblies and Additional costs — each with its own subtotal and a count of how many items are behind it. Expand the Additional costs line and every attached cost rate is listed as name · quantity unit × rate with its line cost.

The Additional costs line is always shown, and reads $0 when nothing is attached — the same way the two lines above it read $0 for a bill with no materials.

Under the three lines sits:

Total cost per unit = materials + subassemblies + additional costs

and, when the bill is linked to a priced variant, a Selling price and a Margin badge measured against that total. A bill whose margin dropped after you attached labour was always making that little — you just couldn’t see it. (A bill with no price shows no margin row at all, rather than a meaningless 100 %.)

An assembly BOM shows the same information on its own Overview tab, in a Costs card: Materials, Nested assembly BOMs, Additional costs, then Unit cost (live) and Unit cost (stored). Those last two can differ, and additional costs are one reason why — see below.

How assembly BOM costs roll up

A cost rate attached to an assembly BOM folds into that bill’s live cost, and therefore into the cost of every bill of materials that uses it — automatically, and counted exactly once.

That means the Additional costs card on a bill of materials lists only the cost rates attached directly to it. An assembly BOM’s own cost rates are already inside the Subassemblies subtotal, as part of that assembly BOM’s cost. Adding the two together would double-count them.

Live cost vs stored cost

An assembly BOM has a stored unit cost, written the last time you recalculated it, and that column is materials only — Recalculate writes the live materials cost and leaves additional costs out. So after a recalculation, Unit cost (live) and Unit cost (stored) differ by exactly the additional-costs bucket. That gap is expected, not an error. Work orders close against the stored number; the live number is what the bill costs to make today.