Free and open
The licence costs nothing and the source is public. It covers sales, purchasing, inventory, accounting, projects and the website. What you pay for is the server and the work of making it fit.
Straight answer
What is an ERP, and when does a company really need one?
An ERP is one system where every piece of business data is written once and everything else reads it from there. When a sales rep confirms an order, stock goes down, the invoice comes out of what was delivered, and accounting finds out by itself. That is all it is. The letters stand for enterprise resource planning, which does not help anyone understand it.
Five signs you already need one
The same data gets typed twice
The order is written on a sheet and typed again into billing. Every copy is another chance for the numbers to stop matching.
The numbers do not agree between teams
Sales reports one figure, accounting another, the warehouse a third. The meeting is spent deciding which one is right instead of deciding what to do.
Everything goes through one person
If that person is away, the company does not invoice, ship or buy. That is not a problem with the person: it is a process that lives in their head.
The month-end close takes weeks
Reconciling the bank by hand and building reports by copying balances means always deciding on old figures.
Nobody knows the margin per product
You know what comes in and out of the bank, but not where the profit comes from. Without that, raising a price or dropping a line is a bet.
Three signs you do not need one yet
I say this even though I sell implementations: buying an ERP too early is the most expensive way to tidy up a company.
The process still changes every month
If the way of working is still being invented, automating it freezes a version that will be wrong next month. Stabilise first, automate after.
Nobody has time for the project
An implementation needs the people who know the work, several hours a week, for months. Without that, the system ends up configured by whoever does not do the work.
The real problem is between people
When two teams do not talk to each other, a shared system does not make them talk. It makes them collide faster, which sometimes helps and sometimes does not.
Where Odoo fits in
Odoo is one of those systems, and the one I implement. It comes in two editions that are worth telling apart.
Paid, per user
It adds applications and services Community does not carry, priced by Odoo per user per month. It is worth it when you need something specific that only exists there, not out of habit.
The community
Hundreds of free modules maintained by the Odoo Community Association, covering a good part of what people assume only Enterprise has. I contribute there.
Which one suits you depends on the case, and it is one of the things the diagnostic answers. What never works is deciding on the licence price alone.
What to do with this
If you recognised yourself in the signs above, the next step is not asking five vendors for a demo. It is knowing which stage your company is at, because that is what decides whether the project goes well.