Why kitting and assembly require dedicated accounting
Many Swiss SMEs do not manufacture from scratch; they add value by combining purchased components: they pack promotional sets, prepare maintenance kits, assemble semi-finished products or customise items to order. In the warehouse these activities look similar, but from an accounting and tax perspective they have different implications for inventory, cost of goods sold and margin.
Without an up-to-date bill of materials (BOM) and clear valuation rules, the balance sheet over- or understates inventory, the income statement shows inflated margins, and pricing and discount decisions rely on incomplete data. Swiss accounting standards (Swiss GAAP FER / micro-entity recommendations) also require a true and fair presentation: relevant transformation costs must be capitalised in inventory until the product is sold or delivered.
This guide explains how to set up kitting and assembly in an SME based in Switzerland: from the BOM to valuation methods, from cost tracking to calculating true margin, with practical pointers for users of accounting software integrated with inventory management.
Kitting, assembly and production: what sets them apart
Before defining journal entries and costing methods, align operational language with accounting terminology. Boundaries are not always sharp, but classification guides cost treatment and the depth of the bill of materials.
| Activity | What happens in the warehouse | Typical accounting impact |
|---|---|---|
| Kitting | Grouping distinct items into a single sellable SKU (set, pack, physical bundle) without material structural transformation | Issue components, receipt kit; kit cost = sum of components (+ packaging/labour where significant) |
| Assembly | Assembly that creates a new inventory item with its own identity (including from semi-finished goods) | Multi-level BOM; transformation costs (labour, energy, equipment depreciation) often included in inventory value |
| Production / processing | Process with cycles, scrap, WIP and dedicated production capacity | Cost or management accounting; allocation of production overheads; possible capitalisation of fixed assets |
| Customer-order assembly | Kit or finished product created only after order confirmation (make-to-order) | Kit inventory often minimal; pay attention to timing of transfer of risk (delivery) for revenue and costs |
For most SMEs with small warehouse teams, kitting and light assembly fall under the same internal «factory»; what matters is documenting for each finished SKU which components go in, in what quantities and with which unit of measure, and whether additional costs apply beyond material.
Bill of materials (BOM): minimum structure for SMEs
The BOM is the master document linking sales, purchasing and inventory. Switzerland has no mandatory legal format, but for audit and tax purposes you need traceability consistent with inventory and invoices.
Practical must-haves
- Finished item code and unit of measure (pieces, set, pack)
- List of components with quantity per finished unit and scrap factor if relevant
- BOM version and effective date (critical for seasonal variants)
- Issue warehouse and, if applicable, assembly routing
- Standard cost or latest reference cost for margin simulations
Variants and phantom BOMs
Kits with options (colour, size, optional extras) require variants or alternate BOMs. «Phantom» bills (logical groups with no stock of their own) simplify structure but must not hide real movements: every component must still be issued.
Align BOMs and item master data with the chart of accounts: raw materials, semi-finished goods, finished products and packaging should be distinguishable for analysis and for VAT where relevant (standard vs reduced rate on certain goods).
A common mistake is updating kit selling prices without recalculating the BOM after a supplier price increase. Accounting software linked to stock can flag variances between theoretical cost (BOM) and actual cost (latest purchase or average) before margin erodes silently.
Inventory valuation: permitted methods and operational choice
Inventory must be recorded at the lower of acquisition or production cost and net realisable value (prudence principle, Art. 958c para. 1 lit. 5 CO and Swiss GAAP FER 17). For Swiss SMEs the most common methods remain FIFO and weighted average cost; LIFO is not permitted under Swiss GAAP FER 17; entities presenting accounts under CO only may adopt other issue methods, unless they choose to apply FER.
| Method | When it fits | Kitting / assembly |
|---|---|---|
| FIFO | Slow turnover, volatile purchase prices, few SKUs | Kit cost = sum of FIFO component costs at assembly time; requires lot or receipt-date tracking |
| Weighted average | High volume, many movements, homogeneous components | Component unit cost recalculated on each receipt; kit inherits average cost on issue — simple but less precise on price spikes |
| Standard cost | Target margins and light industrial control | BOM with annual standard; variances (materials, efficiency) posted to income statement at period end |
Full cost of the finished product
Beyond direct material, include in the inventory value of the assembled item transformation costs that can be allocated objectively: warehouse/production hours, set-specific packaging, regulated labelling where applicable. Pure administrative overheads must not be capitalised in inventory; assembly department structure costs may be, if correlated to output volume and documented (allocation by hours or quantity).
At year-end review obsolete items, unsold promotional kits and components dedicated to discontinued variants: any write-downs affect the income statement and correctly reduce taxable profit, avoiding phantom stock.
Warehouse flow and typical accounting entries
The accounting principle is always the same: no cost of goods sold while the product remains in stock. Assembly is a transfer of value between inventory accounts, not immediate consumption.
1. Component issue for kitting. Issue from raw materials / semi-finished to an intermediate «assembly WIP» account or directly to finished goods if the operation is instantaneous. In parallel, record quantities out to align physical and book inventory.
2. Finished item receipt. Receipt at value equal to component cost plus allocated transformation costs. If you also sell the same kit disassembled (component sales), use two distinct SKUs to avoid double counting.
3. Sale or delivery. Only on invoicing (or on delivery if you apply that criterion consistently) transfer cost from finished goods to cost of goods sold. Swiss VAT follows the supply: ensure the invoice description matches the goods delivered (physical kit vs separate assembly service).
4. Scrap and inventory adjustments. Inventory differences after the year-end inventory count, as a rule by physical count for entities keeping ordinary accounts (Art. 958c para. 2 CO), should be analysed: actual losses, picking errors or wrong BOM. Adjust inventory and income statement with a traceable reason for internal or external audit.
True margins: what the calculation includes
List price of the kit minus a rough sum of purchase prices is not a margin. For channel, B2B discount and promotion decisions you need fully loaded costs consistent with the financial statements.
Commercial gross margin
Net revenue (after discounts and returns) minus booked cost of goods sold. Excludes labour not capitalised in stock — useful for quick comparison but can overstate results if assembly is labour-intensive.
Margin after kitting costs
Includes BOM material, packaging, allocated internal hours and marginal logistics (labelling, prepared shipment). Aligned with inventory value: best basis for pricing.
Margin per order / customer
For make-to-order assembly, calculate actual order cost (components issued at that time + hours) against revenue. Avoid generalising from a standard kit when the customer requests customisation.
Also monitor the mix effect: higher sales of low-margin kits can improve turnover and reduce profit. Monthly reports per finished SKU (units sold, average cost, BOM variance) let you act on suppliers or prices before year-end and estimates of federal direct tax and cantonal/municipal profit tax.
Internal controls and year-end close
Auditors, trustees and, on review, the Federal Tax Administration (FTA) rely on documentary evidence. For kitting and assembly, stronger controls reduce late adjustments and disputes in audit.
- •Year-end inventory with separate counts for finished kits and components «reserved» for assembly; reconciliation with warehouse extract and cost accounting.
- •Segregation of duties: whoever creates the BOM should not be the only person approving significant inventory adjustments; in small SMEs, at least owner or trustee approval on variances above a threshold.
- •Transformation cost documentation: timesheets or warehouse activity logs, allocation basis described in notes or internal register.
- •VAT consistency: kits with goods or services potentially subject to different rates require care in qualification under Art. 19 VAT Act (independent supplies, combination with predominant supply of at least 70% of total price, single economic transaction or ancillary supply); keep calculations and commercial terms.
Digitisation with integrated accounting software
Automating kitting and assembly means linking sales orders, pick orders, warehouse movements and accounting entries in one flow. In Accountex, the goal is for every component issue and every kit receipt to generate traceability for the balance sheet and margin analysis without duplicate data entry.
Set up item master data with type (material, finished, kit), versioned BOM and the valuation method chosen for the company. On order fulfilment, the system proposes theoretical picking; picking adjustments feed material variances. At month end, extracts by SKU show valued stock, cost of goods sold and gross margin — data also useful for liquidity (working capital tied up in unsold promotional kits).
For trust firms serving multiple cantonal clients, standardising BOM and inventory reports simplifies closing and reduces misalignment between warehouse system and general ledger — a common scenario when assembly grows faster than administrative processes.
Operational checklist for SME owners
- Classify each finished SKU: pure kitting, assembly or light production.
- Prepare BOM with version, quantities, scrap and units of measure aligned with purchasing.
- Choose FIFO or weighted average and apply it consistently to components and finished goods.
- Define rules for including labour and packaging in inventory cost.
- Align flow sales → picking → invoice → cost of goods sold.
- Plan year-end inventory and write-down of obsolete inventory.
- Review margins by SKU at least quarterly, not only at year-end.
Well-accounted kitting and assembly turn the warehouse from an opaque cost centre into a lever for pricing and liquidity. With a reliable bill of materials, valuation consistent with Swiss GAAP and margins calculated on full cost, Swiss SMEs can grow on bundles and customisation without surprises at year-end.