Search for inventory software and you'll find excellent tools for counting stock. Search for invoicing software and you'll find excellent tools for billing customers. The catch: for a product business, those are the same workflow. Every sale is both an invoice and a stock movement — and when two apps each own half of it, the gap between them becomes your job.
The two-app pattern (and its price)
The pattern is everywhere. Pure inventory trackers handle counts and locations but can't bill anyone, so you pair them with an invoicing app. Suite vendors sell inventory and accounting as separate products that "integrate" — which means a second subscription, a sync to configure, and two support teams that each point at the other when a number is wrong. Either way you pay twice: once in money, and once in the daily friction of re-entering or reconciling data.
Where split systems actually break
Integrations fail quietly. An invoice voids in the billing app but the stock deduction stays. A price changes in one system a week before the other. A customer's balance says one thing in accounting and another in the sales report. None of these announce themselves — you find them during a count, an audit, or an awkward phone call with a customer who was billed twice.
What "built in" should actually mean
A real all-in-one isn't two modules under one login. The test: when you write a sales invoice, does stock decrease and the customer's balance update in the same transaction — and if you cancel that invoice, does everything roll back by itself? If the answer involves a sync job, a webhook, or "usually within a few minutes", it's still two systems.
The checklist for product businesses
Look for: sales and purchase invoices that post stock automatically; customer and supplier accounts with running balances and receivables aging; an order → delivery note → invoice chain so nothing ships unbilled; cash and bank tracking so payments land against the right account; and barcode stocktakes so the numbers stay honest. That set covers the daily loop of a shop, wholesaler or parts business — without a second app.
What it should cost
The two-app pattern typically stacks a mid-tier inventory plan on top of an accounting plan, and per-user pricing multiplies both. An integrated system should price the whole loop as one plan — which is exactly the gap Stokpax targets: inventory, invoicing, customer accounts and cash from $29/month, in the browser, with a 7-day free trial.
If you're currently juggling a stock tracker and a billing tool, the switch is smaller than it looks: your items, customers and opening balances import from CSV, and from day one every invoice keeps the stock and the balances right on its own.