Off-the-shelf or custom: how do you actually decide?

Someone put this to me almost accusingly, and they were right to: why are we spending so much money on software where we could just have something off the shelf that costs a few hundred quid a month?

Often they should. I have talked people out of builds with that exact reasoning. Here is how I decide.

Buy off the shelf when

• Your process is normal. Invoicing, payroll, email marketing, basic CRM — thousands of businesses do these almost identically, and someone has already built it better than I would.
• You can live with changing how you work to suit the tool. This is the real cost of off-the-shelf, and it is usually worth paying.
• The problem is not the thing you compete on.

Build when

• The process is the reason customers choose you. If it is your edge, do not sand it down to fit somebody else's form.
• You are paying for eleven modules to use two, and the two do not quite work.
• You have already bought the off-the-shelf tool and built a spreadsheet next to it to make it usable. That spreadsheet is a specification, and it is telling you something.
• Nothing exists, because your industry is small enough that nobody has bothered.

The middle path most people miss

Somebody asked me: is it better to build a custom CRM, or get something off the shelf and then build on top of that?

Usually the second. Buy the boring parts — contacts, calendar, permissions, the things you gain nothing from owning — and build only the piece that is genuinely yours. It costs a fraction of a full build and it does not saddle you with maintaining a login system for the next decade.

The question that settles it

If we bought the standard tool and changed how you work to match it, what breaks? If the answer is "nothing much, people would grumble for a month" — buy it. If the answer names a specific customer promise you could no longer keep, now we are talking about a build.