Custom software vs an ERP: when each one makes sense

An ERP is a system of record: accounting, invoicing, inventory, purchasing, receivables and payables. It does the same thing for thousands of companies, and that is exactly why it is good at it. Your invoices are issued the same way everyone else's are.

Custom software does what only your company does: how you configure a product, how you quote, who approves credit, how you follow up on a warranty. That is where a generic system makes you adapt to it, or handle things outside of it, almost always in Excel.

So the useful decision is not which of the two, but which processes go into each.

SAP Business One, Odoo, NetSuite and their peers handle what is the same in every company, and keep it current for you:

• Accounting and the period close.
• Invoicing, including the tax-authority changes that keep coming.
• Payroll, where the package includes it.
• Inventory, purchasing and warehouse with standard rules.
• Receivables, payables and banking.

If your operation fits those processes the way the system ships them, an ERP is the cheapest and fastest answer. Rebuilding that as custom software rarely makes sense, and we say so even though custom software is what we sell.

The limit shows up in whatever is particular to your business. The cases we see most:

• Configurable products: options that depend on each other and that a flat catalog cannot express.
• Quotes with commercial rules of your own: customer, volume or bundle discounts, and approvals when someone goes below margin.
• After-sales: warranties by serial number, service, spare parts and the history of every unit sold.
• Portals for your customers or your dealer network, with different prices and permissions per account.
• Processes that cross departments (sales, credit, warehouse, service) and that live in ERP modules that do not talk to each other.

Many ERPs can be customized to cover this, but every customization is paid for twice: when it is built, and at every system upgrade, when someone has to check it still works.

Neither column wins everywhere. That is why the answer is usually both, each doing its own job.

The ERP keeps accounting, invoicing and book inventory. The custom platform takes what happens before and after: the catalog, the configurator, the quote, the approvals, the customer portal and after-sales. The data that has to move between them does, through an API or an export.

That is how the Kit Machinery platform works, for one: a rules-engine configurator, quoting, credit approval, contracts, a customer portal, warranty, service and spare parts, all on the same record of the machine that was sold.

A simple test: if a process works the same in your company as in your competitor's, it probably belongs in the ERP. If it is the reason customers buy from you, it is probably worth building to fit.

1. List the processes that generate revenue and mark where each one lives today: in the ERP, in Excel, on WhatsApp or in someone's head.
2. Ask your ERP vendor how they would handle the ones that live outside it, with which module or customization, and what happens to that customization at the next upgrade.
3. Compare the total cost over three to five years, not the starting price: per-user licenses, customizations, maintenance and your team's time spent working around the system.

That last point is the one most often skipped. Gridarco was founded by a controlling analyst: the cost that never appears on the quote, the hours your team spends re-keying data, is usually the largest one.