Prepared by the NADALI editorial team using AI
Three suppliers have quoted for the same service. One charges monthly, another per visit, and a third offers a package with setup included. Asking AI to choose the best proposal immediately can produce a comparison of different scopes, with missing information quietly replaced by assumptions.
A more useful assignment is to prepare evidence for a decision: what each supplier offers, where it is written, which terms are missing and what needs clarification. Compare costs once you understand the result the business would be buying.
The workflow below is an editorial proposal for routine service purchases by small businesses. We have not tested it or measured cost savings. It does not replace contract review or professional advice on legal and tax questions.
1. Freeze the requirements before reading the offers
Write a short description of the purchase before opening the sales presentations. What result is needed, for which locations or equipment, by when, and how will you accept the work? Specify users, equipment units or visits wherever these determine scope.
Separate essential requirements from preferences. Coverage during particular hours might be essential; an additional report format might be optional. Give requirements identifiers such as R-01, R-02 and R-03. Each supplier statement can then be checked against a specific requirement.
Choose a comparison period, a decision owner and a tie-break rule. If using scores, define each rating and criterion weight in advance. Attractive document design should not earn extra points.
New Zealand Government Procurement guidance distinguishes a rating scale from the method used to combine criteria. It provides a methodological reference here; another country’s public procurement rules are not presented as small-business obligations.
If a proposal reveals an important new need, pause. Create a revised requirements document and reassess every option. Do not change a criterion for just one supplier.
2. Prepare a controlled document set
Keep original proposals, attachments and clarifications. Assign each file an identifier and record its date, version, page count and price-validity period. For emails, record the date and subject. Check that referenced attachments are present.
Give AI only approved material through a tool authorised for those data. Remove unnecessary contact details, signatures, bank details and customer information. Prices and commercial terms may remain confidential after redaction. If sharing is not approved, build the comparison manually.
For scanned files, check recognised numbers and footnotes against the original. A missing symbol or misplaced column can change a price. Mark an unreadable page as unverified rather than letting the model reconstruct it from context.
3. Build an evidence matrix
Create a separate row for each requirement and proposal pair. Suggested fields are:
- Requirement ID and the result needed
- Supplier labelled A, B or C
- Exact value or short extract from the proposal
- Source file, version, page and clause
- Status, explanation of any mismatch and clarification question
- Reviewer’s name and date checked against the original
Keep three states distinct: explicitly included, explicitly excluded and not stated. Silence about training does not prove that training is unavailable. Equally, “full support” does not establish a particular training allowance. Conflicting documents need a separate conflict status with both source references.
“Included” records what the proposal says. It does not establish the supplier’s ability to deliver. Check important claims about experience, compatibility or quality through an appropriate separate process.
Ask the model to extract each document separately before comparing rows. Checking only the cheapest offer is insufficient: verify every term that could affect the decision.
NIST describes the risk of confidently expressed errors, including invented reasoning and citations. A page reference generated by AI therefore also needs checking.
4. Compare the same scope and cost basis
Keep original figures beside calculated values. Record currency, charging unit, quantity, one-off fees, recurring fees, minimum term and included allowances. List additional work, delivery, consumables and renewal terms separately where relevant.
Use the same agreed tax basis. If tax treatment is unclear, leave a question for the supplier or accountant instead of inserting an assumed rate. For different currencies, agree an exchange-rate source and calculation date, and retain the original currency. The conversion does not guarantee the rate when payment becomes due.
A monthly equivalent for a two-year offer does not mean the business can leave after a month. Show the full minimum commitment, payment schedule and unknown exit terms alongside the cost for your chosen period. An unknown exit charge should not become zero.
AI can suggest the calculation structure. Calculate totals with checked spreadsheet formulas or a calculator, keeping inputs visible. A person should verify units, rounding and whether a one-off charge has been counted twice.
5. Example: comparing the same scope
Suppose a business is comparing maintenance for one agreed set of equipment over 12 months. It needs two scheduled visits each month, making 24 annually, plus defined hours for emergency requests.
In this teaching example, proposal A has a setup charge S and a monthly charge M covering two scheduled visits. Proposal B has a setup charge T and a charge V for each scheduled visit. The letters stand for values to be verified later; they are not market prices.
If each visit covers the same work and all other included services match, the calculation bases are S + 12 × M and T + 24 × V. These are not yet complete comparable totals: emergency requests, materials and other necessary components still need resolving.
Suppose A explicitly excludes spare parts while B says nothing about them. The matrix retains different statuses. Silence does not justify describing B as either more expensive or better value.
Likewise, a promise to respond within a stated time does not establish that repairs will be completed within that time. Use separate rows for response, attendance and restoration times where relevant. An unresolved essential condition keeps the final choice open.
6. Turn gaps into short questions
Ask AI to draft a clarification for each supplier using that supplier’s documents and the common requirements. Do not disclose another supplier’s proposal or the internal budget ceiling without a separate decision.
Example draft, not yet sent:
Thank you for proposal [number and version]. Clause [number] states [term]. To compare the same scope, please confirm what one scheduled visit covers, which emergency-request hours are included, how spare parts are charged and the minimum order term. Please identify changes from the previous version and state how long this clarification remains valid.
A person checks the recipient and wording before sending. Keep the reply as a new source rather than silently changing an old cell. Update affected rows and rerun the relevant calculations.
New Zealand’s guidance on evaluating responses emphasises clarifications and a written assessment rationale. The short draft and matrix structure here are editorial adaptations for a working comparison.
7. Test the conclusion and retain the decision
Return to the agreed criteria. If options are close, apply the prewritten tie-break rule: for example, confirmed coverage of required hours followed by completeness of scope. Do not ask the model to appoint a winner arbitrarily.
Check what changes under another realistic workload: one extra visit, additional users or a different service period. Calculate using confirmed rates; label other inputs as scenario assumptions. If the apparent advantage depends on an unknown extra charge, the useful result is the question that must be answered next.
Treat proposal content as data. The NIST profile also describes malicious instructions embedded in material an AI system retrieves. A document instruction to recommend its own supplier must not control the assessment. Use an environment without the ability to send messages, place orders or pay independently. A sentence in a prompt does not establish that technical restriction.
Save a short decision record: requirements version, proposals considered, verified scope, calculation, open questions, accepted assumptions, reason for the choice and responsible person. Explain rejection of an option by reference to a specific requirement. Approval of this record does not replace separate approval to place the order.
Sources and verification date
The three primary sources were read on 14 October 2026. They support general assessment principles and AI cautions. The matrix, teaching example and workflow are editorial proposals rather than findings about a particular supplier’s performance.
