# Invoice 2026/09/014 **Seller:** EPSI sp. z o.o., ul. Bura 21, 00-000 Burowce, NIP PL9998877666 **Buyer:** Northwind Logistics GmbH, Hafenstraße 8, 22222 Hamburg, USt-IdNr. DE881188118 **Issued:** 2026-09-03    **Delivered:** 2026-08-31    **Payment due:** 2026-09-17 ```vmark vat = 23% early_pay_disc = 2% fx_eur = 4.2650 ``` ## Services rendered | Item | Unit | Qty | Rate | Net | VAT | Gross | |----------------------------|-------|----:|--------:|---------:|--------:|---------:| | Discovery workshop | day | 2 | 1800.00 | 3600.00 | 828.00 | 4428.00 | | **Backend implementation** | hour | 64 | 220.00 | 14080.00 | 3238.40 | 17318.40 | | Code review retainer | month | 1 | 2500.00 | 2500.00 | 575.00 | 3075.00 | | On-call support | hour | 12 | 260.00 | 3120.00 | 717.60 | 3837.60 | ```vmark #lines Net = Qty * Rate VAT precision 2 = Net * vat Gross = Net + VAT net_total = SUM(Net) vat_total = SUM(VAT) gross_total = SUM(Gross) ``` Net of tax the engagement comes to **23300.00** PLN. VAT at 23% adds **5359.00** PLN, giving a total due of **28659.00** PLN. ## Payment schedule | Milestone | Share | Amount | Due | |---------------------|------:|---------:|------------| | Signature | 30% | 8597.70 | 2026-09-10 | | Delivery of backend | 40% | 11463.60 | 2026-10-15 | | Acceptance | 30% | 8597.70 | 2026-11-30 | ```vmark #schedule Amount precision 2 = Share * lines.gross_total covered = SUM(Amount) ``` The three milestones account for **28659.00** PLN. ## Payment terms ```vmark #terms early_pay_total precision 2 = lines.gross_total * (1 - early_pay_disc) early_pay_saved = lines.gross_total - early_pay_total eur_total precision 2 = lines.gross_total / fx_eur ``` Settlement within 7 days qualifies for a 2% early-payment discount, reducing the amount due to **28085.82** PLN — a saving of **573.18** PLN. For reference, the gross total is approximately **6719.58** EUR at the ECB reference rate of 4.2650 PLN/EUR recorded on the delivery date. ## Reconciliation ```vmark #recon scheduled = SUM(schedule.Amount) variance = lines.gross_total - scheduled assert variance == 0 ``` Scheduled instalments total **28659.00** PLN against a gross invoice value of **28659.00** PLN, leaving a variance of **0.00** PLN. --- ## Appendix — how this document computes Everything above renders as ordinary Markdown. The mechanics are four ideas. **A `vmark` block declares formulas for the table above it.** The block carries the sheet's identity as `#lines`, `#schedule` and so on. A block with no identity — the one near the top of this file — declares document-level constants that every sheet can read, which is why `vat` and `fx_eur` resolve without qualification. **Columns are uniform.** `Net = Qty * Rate` is one rule applied to every row of the sheet, not a formula per cell. Columns not named in the block — `Item`, `Unit`, `Qty`, `Rate`, `Share`, `Due` — are inputs, typed by a human and never overwritten. There is no per-row exception and no totals row inside a table. **Aggregates are scalars, declared in the same block.** `net_total = SUM(Net)` collapses a column to a single named value that lives outside any grid. This is what replaces the totals row, and it is why the `#recon` block needs no table of its own: a sheet is a namespace, and a table is optional. **A comment anchor materialises a scalar into prose.** `` binds the bold number in front of it to that name. The comment is invisible in every Markdown renderer that permits raw HTML, so the sentence reads normally while the number stays machine-checkable. Sheets address each other by qualified name, as `#schedule` does when it reads `lines.gross_total` and `#recon` does when it aggregates `schedule.Amount`. A foreign column is a vector, so it is legal only inside an aggregate — bare `schedule.Amount` in a column formula is an error, because the two sheets have no reason to share a row count. **An `assert` states an invariant.** `assert variance == 0` in `#recon` is not a binding — it stores nothing and `fmt` never touches it — but `check` evaluates it and fails if it is ever false. Without it, a payment schedule whose shares stop summing to the invoice total would leave a non-zero `variance`, and `check` would still pass: every number would agree with its own formula. The assertion is what turns "the reconciliation is computed" into "the reconciliation is enforced". The payoff is the last section. `visimark check` recomputes every formula and exits non-zero if any stored number disagrees, so an arithmetic error in this invoice fails CI instead of reaching the buyer — whether a human or an agent wrote it. ### Deliberately unresolved A percent literal is a number: `23%` and `0.23` are the same value, so `vat` may be written either way and arithmetic needs no special case. Because the tool writes only computed cells, an input written as `30%` stays `30%` forever — the display-format layer that Excel needs never has to exist here. Dates are settled: ISO 8601 calendar dates, `YYYY-MM-DD`, and nothing else, so no date here can mean two things. Thousands separators in cells, decimal versus binary floating point, and rounding policy remain open. See `example-invoice-drift.md` for what the checker does with each.