Tool Build vs Buy Worksheet
A worksheet for comparing a custom build with an existing tool using workflow fit, cost, control, time and maintenance.
Working record
| Check | What to do | Evidence to retain |
|---|---|---|
| Requirements | Describe what the user must accomplish and the condition under which the result is acceptable. Separate an essential outcome from a preferred feature. | Observable acceptance criteria and a test case. |
| Purchase cost | Separate one-off implementation, recurring operation and exit costs. Check each billing unit against the source quotation. | Cost line, source, currency, period and exclusions. |
| Build effort | Include discovery, engineering, testing, documentation and maintenance when estimating a custom build. | The build effort record, its source and the person responsible for resolving missing evidence. |
| Control | Identify the configuration, data and operating decisions the business must retain under its own control. | The control record, its source and the person responsible for resolving missing evidence. |
| Maintenance | Identify updates, monitoring, backups and incident responsibilities. Include the work required after initial launch. | Maintenance schedule, owner and recovery test. |
Review the decision
A worksheet for comparing a custom build with an existing tool using workflow fit, cost, control, time and maintenance. Keep requirements, purchase cost, build effort attached to the conclusion so the next owner can challenge the assumptions. Resolve missing evidence before treating this record as approval.
Continue the decision
How to Compare Software Without Turning the Page Into a Feature List · How to Choose Business Software.
Calculation and source notes
Keep the displayed formula, input units and model scope with the result. Corrections or questions can be sent through the request section on this page.
Content updated: October 11, 2026