Choosing a software supplier rarely goes wrong during the sale. It goes wrong eighteen months later, when somebody asks where the source code is, or why a tax rule change requires a new release of the application, or who approved a change nobody can trace.
All of those are predictable. This article collects the twelve questions that prevent them — asked before you sign, while you still have leverage.
The commercial questions
1. Who owns the source code when the project ends?
The right answer is "the client", in writing, in the contract. If the answer is "we license you the use of it", you are renting rather than buying, and the cost of leaving grows every year. Ask to see the clause, not the verbal assurance.
2. What happens if our relationship ends?
Ask for the concrete exit plan: data export in an open format, handover of repositories, infrastructure documentation, credential transfer, and a transition period defined in days. A confident supplier writes this without hesitating. A supplier who resists is telling you something important.
3. Who will actually write the code?
The team in the sales presentation is not always the team that delivers. Ask for names, seniority and percentage allocation. Ask whether any work is subcontracted, and to whom.
4. How is the price calculated, and what triggers an extra cost?
Fixed price, time and materials, or a dedicated team — each model has a legitimate use. What matters is knowing what counts as a scope change and who decides. Ask for a concrete example: "if we need to add a field to an existing form, is that included work or is it quoted?"
The regulatory questions — specific to Angola
5. Are tax rules in code or in configuration?
This is the single most revealing question on the list. If VAT, withholding or approval thresholds are written into the code, every legislative change becomes a development project, with the timeline and cost that implies.
Worse: if an old invoice is reissued, it is recalculated under today's rule rather than the one in force on its issue date. That is not a technical detail — it is an inconsistency that surfaces during an inspection.
The answer you want involves effective-dated configuration: rules have a start and end of validity, and a document is always calculated with the rule in force on its date.
6. How do you handle SAF-T and electronic invoicing?
The SAF-T file should be exported from the same entries that feed internal reporting — one source, not two. If the supplier describes a separate process for "preparing the SAF-T", you will have two accounting truths and a reconciliation job every month.
On electronic invoicing: ask directly what the software's certification or validation status is with the AGT, and ask for the answer in writing. It is a legitimate question and evasion is informative.
7. If we operate in oil and gas, what do you know about local content and the ANPG?
The local content regime and supplier qualification should be calculable and auditable inside the system, not argued in a spreadsheet before each reporting cycle. If the answer is vague, the supplier will be learning at your expense.
8. Where is the data hosted, and can we choose?
Since the national data centre opened in April 2026, hosting on Angolan soil has stopped being impractical. That does not make it automatically the right choice — ask about the contracted SLA, the facility's certifications, and where the geographic replica sits.
The engineering questions
9. Can I delete a transactional record?
The right answer is "no". Documents should be cancelled, voided, reversed or versioned — never removed. A system where rows can be edited or deleted has an audit trail worth exactly as much as the good faith of the last person who touched it.
10. How does the audit log work?
Look for three properties: append-only, immutable to ordinary users, and carrying an identifier that lets you follow a complete flow from request to accounting entry. The follow-up question that separates serious answers from the rest: does the application account have write permission on the audit tables? If it does, immutability depends on the code behaving.
11. What test evidence ships with a delivery?
Do not ask "do you test" — everybody says yes. Ask what is delivered with each feature, and ask to see it. Permission tests and negative-case tests are the ones that count in a system with access profiles; they are also the first to be cut when a deadline tightens.
12. What happens when you do not know a regulatory rule?
The answer you want is that the function stays blocked and configurable until somebody confirms the rule against a primary source. The answer you do not want is a plausible-looking default, because that value goes into production and nobody looks at it again.
How to run the evaluation
Cut to three suppliers and ask all twelve questions of each, in writing. Comparable answers tell you more than any presentation.
Then ask each one to show software running against realistic data. Not a prototype, not slides. Thirty minutes of a real system answers what two weeks of proposals do not.
And phone a reference from a project of the same type — not the most famous client, the project most like yours.
If you want to see who operates in this market and what each one specialises in, we collected that in software companies in Angola: who does what. And if you want to put these twelve questions to us, our answers are in writing — including the ones that do not flatter us.