Custom App, Off-the-Shelf Software, or Spreadsheet: How to Decide

Short answer: use a spreadsheet as long as the work is small, handled by one or two people, and the workflow is not yet fixed. Use off-the-shelf software (ERP, SaaS) when the need is common, such as accounting or HR, and already served by a mature product. Build a custom app when your workflow or service is distinctive, cannot be found in ready-made products, and you want a system you can own and continue developing.

Almost every internal system starts as a spreadsheet. Problems arise gradually: files get bigger, versions multiply in email, and working rules live only in one person’s head. At that point there are usually three options: tidy up the spreadsheet, buy off-the-shelf software, or build your own application. This article compares the three on the factors that most often decide the question.

Comparing custom apps, off-the-shelf software, and spreadsheets

Aspect	Custom app	Off-the-shelf software (ERP, SaaS)	Spreadsheet
Fit with your workflow	Designed around your workflow, including distinctive rules	You adapt how you work to the available features	Flexible at first, but the rules live only in users’ habits
Access rights and change history	Role-based login and activity logs built to your needs	Usually available, within the limits of the product’s options	Limited to file sharing
Ownership	Source code and usage rights belong to you	Usage rights are rented or bought, the code is held by the vendor	The file is yours, but it is not a system that can be continued
Time until use	Usually 3 to 6 months for mid-sized scale	Faster if the need matches the built-in features	Immediate
Running costs	Build cost upfront, then maintenance if you choose it	Subscription or license, often growing per user	No need to buy dedicated software, but more and more team time is absorbed
As data and users grow	Capacity can be added without rebuilding	Follows the product’s plans	Slows down and is prone to typos

When is a spreadsheet still enough?

A spreadsheet is not a mistake. It is the right choice as long as these three things hold:

• Few users. One or two people who know each other’s changes.
• The workflow is not yet fixed. You are still finding the way of working that fits best, and changing columns every week is still reasonable.
• The data is not sensitive. There is no need to restrict who sees which rows.

As soon as one of these three changes, the hidden costs of a spreadsheet start to show: time spent reconciling versions, typos discovered only at month end, and dependence on the one person who understands the formulas.

When does off-the-shelf software make more sense?

Off-the-shelf software excels at needs that are the same across many companies: accounting, payroll, HR, email, and document collaboration. A mature product has already thought through the common rules, updates, and basic security, and you can start within weeks.

What to weigh before buying:

1. How far your way of working has to change. If the team must take a detour for one important step, you pay for it every day.
2. Cost per user over three years. Count not only today’s price but also what happens as the number of users grows.
3. How to get your data out. Make sure the data can be fully exported if you ever switch products.

When is a custom app worth building?

A custom app is worth it when your workflow or service is distinctive and is in fact what sets you apart. Examples include public services that must follow specific rules, multi-layer approval processes that do not exist in ready-made products, or systems that must connect several units with different access rights.

Two examples from Legia’s portfolio:

• PPID BNPT Public Information Portal. Applicants must pick the correct route among information categories that sound similar, and can then track the status of their own request without calling an officer. A flow like this follows public information disclosure regulations, not the common pattern of ready-made products.
• JDIH BNPT Legal Document Portal. Users search for documents from fragments of information (type, area of law, or year), and a regulation’s validity status must be readable together with the document, including the regulations that amend and revoke it.

If you choose to build, make sure three things are written into the contract: source code owned by the company and kept in a repository under your name, documentation sufficient for another team to continue, and a maintenance plan for after the application goes into use.

Costs that are often forgotten in each option

A price comparison on paper rarely counts everything. Include the following items before deciding:

• Spreadsheet: working hours spent reconciling versions, checking formulas, and fixing typos. Count it per month, then multiply by twelve.
• Off-the-shelf software: the cost of additional users, modules that turn out to be sold separately, training, and customization done by product consultants.
• Custom app: maintenance after the app goes into use (security updates, fixes, small adjustments), the server or cloud service the app runs on, and the process owner’s time during requirements mapping.

The last item is often underestimated: a custom app is only as good as the understanding of the requirements, and that understanding comes from the people who run the process every day.

Five questions to decide

Answer the following five questions together with the process owner, not only the IT team:

1. Is this workflow the same as what most companies use, or distinctive to us?
2. How many people will use it in two years, and do they need different access rights?
3. Do we need to know who changed what and when?
4. Does this system need to connect to other existing systems?
5. If the product vendor shuts down or raises prices, how hard would it be for us to move?

If most of the answers are “common,” start with off-the-shelf software. If most are “distinctive,” and the system will be used for years, a custom app is usually more economical in the long run.

Frequently asked questions

Do you have workflows that spreadsheets and email can no longer hold? See Legia application and software services, or schedule a consultation through the contact page.