Off-the-shelf or custom software? How to decide

A development firm writing about this question has an obvious interest in the answer, so here is ours up front: most businesses should buy most of their software. Accounting, payroll, email, CRM for a conventional sales process — buy them. The question is what to do about the processes where the products do not fit.

When buying is right

• The process is standard in your industry and not how you compete.
• A product fits the process without changing the parts that matter.
• You would rather adapt the process to the product than pay to adapt software to the process.
• The vendor is stable and its roadmap is heading where you are.

When custom software earns its cost

• The process is how you compete. The way you schedule, quote, validate or serve customers is part of why you win work. Flattening it to fit a product gives that away.
• The fit gap is in the critical part. A product that fits most of the process but not the part where errors are expensive is not a good fit.
• You would be gluing several products together. Three subscriptions, two integrations and a spreadsheet to reconcile them is a custom system — just an unreliable one.
• The rules change often. Regulated processes, programme rules, pricing logic. If every change waits on a vendor’s release cycle, owning the rules is cheaper.
• The data has to be yours, in your shape. Reporting, retention and audit sometimes need a structure no product offers.

“Our ERP is too rigid”

This is one of the most common complaints, and the instinct to replace the ERP is usually wrong. ERPs are rigid because they hold the financial and operational record, and that rigidity is what makes the numbers trustworthy.

The better question is whether the need belongs inside the ERP at all. Often it does not: a customer portal, a field app, an approval flow, a planning tool. Those can be built beside the ERP, reading and writing through its supported interfaces, so the ERP stays the record and the business gets the flexibility. Customising the ERP core is the expensive option — it complicates every future upgrade.

The third option: buy and extend

Many of the best answers are both. Buy the platform for the standard eighty per cent; build a thin custom layer for the part that is yours; integrate them properly. This applies to warehouse management systems, field service products and ERP modules alike. It only works if the integration is designed with care — see systems integration.

Running a fit-gap honestly

1. List the processes the software must support, including the exceptions.
2. Mark which ones are critical — where an error costs money, customers or compliance.
3. Score each product against each process, using your real scenarios rather than the vendor’s demo.
4. Weight the gaps by criticality. A gap in a critical process outweighs many small conveniences.
5. Price the workarounds. Every gap a product leaves is filled by people, spreadsheets or customisation, and each has a cost.

Compare total cost, not price

A subscription looks cheaper than a build, and often is. But include configuration and implementation, integration with your other systems, the people-time spent on workarounds, and what it costs to change your process to fit. On the custom side, include hosting, maintenance and future change. Our guide on what drives the cost of custom software covers that side.

If the answer for part of your operation is custom, that is what our custom software work is for — and the specification we write first includes the fit-gap that tells you whether you should be buying instead.