One system. Only the parts you use.

Customers & organizations

Every company and contact you deal with. This one is not optional, because a purchase order needs a supplier, an order needs a customer, and a work order needs to know who it is for. What is optional is whether you manage the relationship here or somewhere else.

Organizations

Companies you buy from and sell to, with their contacts and documents

Contacts

People, their roles, and the history against them

Referenced everywhere

One record the rest of the system points at, never a second copy

Inventory & purchasing

What you hold, where it is, what is on order and what it cost. Movements are recorded in an append-only ledger, so a correction adds an entry rather than overwriting one — the question is never what the system thinks you have, it is what happened and when.

Stock levels

Real quantities by location, in the unit each item is measured in

Receiving & transfers

Goods in, goods moved, goods issued out

Purchase orders

Raised against real demand, received against real stock

Lots & serials

Identity that follows the goods through and out the door

Items & quantities

Your product types modeled as real structures rather than rows in a generic item table, and every quantity carrying its unit. Buy steel by the kilogram, issue it by the sheet, cost it by the square meter — and have all three agree.

Product types

Each type its own structure, with its own fields and its own workflow

Units

The unit travels with the number, from purchase through to cost

Conversions

Held once, applied everywhere, refused when they cannot be made