Replacing aging business software

Many companies still run on software installed fifteen or twenty years ago. It works, the teams know it, and nobody wants to touch it. The day the only technician who understands it retires, or the server it runs on fails, the question becomes urgent. It is better to deal with it before that happens.

Warning signs

Old software is not a problem in itself. It becomes one when several of these signs add up:

• the vendor is gone or no longer develops the product;
• the software requires an operating system that is no longer supported. For example, Microsoft states that Windows 10 support ended on October 14, 2025: a computer that no longer receives security updates is an open door;
• only one person knows how to run it or fix it;
• teams surround it with spreadsheets to do what it cannot;
• it does not connect to anything: not the website, not accounting, not a mobile tool;
• it only works at the office, even though your teams also work on the road or remotely.

Three possible strategies

I almost always recommend gradual replacement. You start with the most painful module, or the easiest one to isolate, put it into production, check it, then move on to the next.

While both systems coexist, a temporary sync keeps them consistent: for example, customers created in the new tool are copied into the old one as long as invoicing still happens there. This sync has a cost, but it avoids the “big bang” cutover, where everything changes on the same Monday morning and the smallest oversight brings operations to a halt.

Recovering hidden business rules

The real risk in a replacement is not development. It is forgetting a rule the old software applied silently: a discount calculation, a rounding rule, an alert, a mandatory numbering sequence. To recover them, scoping draws on three sources:

• the users, by observing how they actually work, not just by interviewing them;
• the data, whose analysis reveals edge cases and inconsistencies;
• the documents it produces (invoices, delivery notes, reports), which must be reproduced exactly when they have legal or contractual value.

This is also when you decide which data to migrate. The method is detailed in migrating your data from old software.

Budget and timelines

The ranges below exclude VAT and cover a first version running in production, data migration included.

If the old tool is an Access or FileMaker database, see the page on modernizing an Access or FileMaker application. For a first range based on your features, use the estimator.

Before pricing a replacement, an audit ($660 (€589)excl. VAT for the express version, $2,300 (€1,990)excl. VAT for the full version) inventories what the software really does, the state of the data and its dependencies. It is the most cost-effective investment in the whole project.

When to keep your current software

Replacing software that works carries a cost and a risk. I advise keeping it, and securing it, if:

• it covers the need properly and your teams are satisfied with it;
• it is still maintained by its vendor, with regular updates;
• it can be extended with a modern tool for new needs (mobile, customer portal);
• your business is heading into a busy period that leaves no room for change.

In those cases, the right option is often extending your existing software without replacing it, by adding what is missing around it.

How the replacement works

1. Audit: inventory of functions, data and dependencies.
2. Scoping (1 to 2 weeks): choice of the first module, business rules written down, fixed quote.
3. Mockups tested by users who know the old tool well.
4. Development in batches, with both systems running side by side for a while.
5. Module-by-module switchover, with data migration and training.
6. Shutdown of the old software once everything has been taken over and checked, with the history archived in a readable format.

The source code of the new tool is transferred to you once paid in full. That is your guarantee of not ending up in the same situation fifteen years from now. My overall approach is described on the business apps page.