9. Assumptions and Open Inputs
This idea came from row E6 of the 30 Sept 2026 micro-SaaS idea catalog, not from a founder's brief. No target customer, price, geography, stage, team or traction was supplied. Here's what I assumed, and how the verdict changes if each assumption is wrong.
9.1 Assumptions made
| Input | Assumption used | If actually different… |
|---|---|---|
| Hours per week available | Two columns: ~15 hrs/week and full-time | Under ~10 hrs/week, you're unlikely to be listed and reviewed before spring 2027. The odds fall toward the "as described" column. |
| French-language capability | Available, yourself or through a paid part-time partner | Without it, multiply the odds by ~0.6. French merchants and accountants won't trust English-only compliance support. |
| Founder location | Not stated. It could be outside France. | Location doesn't matter for a Shopify app, but French business hours for support do. A French or EU entity helps with trust and with signing a partner PA. |
| Target customer | French Shopify merchants, €100k–5M revenue, B2B orders preferred | If you have access to French accountants, start with them as the channel from week 1, which raises the odds. |
| Price | €19 / €39 / €89 a month, blended ~€32–34 | Below a €25 blend, the churn and margin checks fail. Above €45, free PAs win the comparison for most B2C-only stores. |
| Partner PA cost | 8–15% of revenue (not verified) | At ≥15%, Tier B's ≥80% margin fails. At ≤8%, margin is ~88%. |
| Mandate date | 1 Sept 2027 holds for small and micro businesses | A slip to 2028 moves the wave outside the window. Every rung from $5k up falls by about half. |
| Shopify's behaviour | No native PA partnership before mid-2027 | A native deal before spring 2027 halves every rung above $3k. See 05. |
| Stage and traction | Idea. No code, no users. | Any paying merchants change the conversation from judgment to evidence. |
| Exchange rate | €1 ≈ $1.15 (not verified) | Customer counts in the ladder move by the same percentage. |
9.2 Inputs that would change the verdict most (please supply)
- Hours per week you can hold through Oct 2027.
- French-language ability, or a named person who can do French support.
- Access to French accountants or Shopify agencies. One accounting firm with 30 e-commerce clients is worth months of SEO.
- Shopify app experience (any published app, any reviews).
- Partner PA quotes after the day-1 emails: price per transaction, minimums, e-reporting support, price lock.
- Budget for an adviser (~€500–1,500 for a review) and professional indemnity insurance.
- Whether you'd accept selling the app to a PA as a good outcome. It changes how you build (clean partner abstraction, documented data model).
9.3 Definitions used throughout
- PA (Plateforme Agréée): an approved platform registered with the French tax authority (DGFiP). All French B2B e-invoices and e-reports must pass through one. 149 were registered on 22 Sept 2026.
- E-reporting: periodic transmission of transaction data that isn't a domestic B2B e-invoice, mainly B2C sales and international sales, plus payment data for some services.
- VAT franchise (franchise en base): the VAT exemption for small businesses. They still e-report, every 2 months.
- Tier A / Tier B: as in the portfolio README.
- Revenue churn: monthly lost MRR ÷ MRR at the start of the month, reported both including and excluding store closures.