invoic-checker

Pure INVOIC plausibility and tariff validation library for German energy market suppliers.

invoic-checker implements the six-check pipeline that invoicd runs automatically against every incoming INVOIC — and that netzbilanzd runs before dispatching to prevent an immediate dispute.

Design constraints

Constraint	Detail
No I/O	All inputs are passed as arguments. No database calls, no HTTP.
No async	Synchronous throughout.
No float money	All monetary comparisons use `rust_decimal`.
Pure functions	`InvoicCheckEngine::check()` cannot fail — it always returns `CheckResult`.

The checks

#	Rule	Outcome on failure
0	Storno reference — `ist_storno=true` must have `original_rechnungsnummer`	`Dispute`
1	Period validity — `rechnungsperiode_start < end`, both within plausible range	`Dispute`
1.5	Zahlungsziel — `faelligkeitsdatum < rechnungsdatum` (invalid) or `> max_zahlungsziel_days` (exceeded; default 30 per §7 Allg. Festlegungen)	`Dispute` or `Warn`
2	Position arithmetic — every `Rechnungsposition` `menge × preis ≈ betrag` (±1%)	`Dispute`
3	Document total — sum of all positions ≈ `gesamtbrutto` (±1%)	`Warn`
4	Tariff match — `einzelpreis` within tolerance of PRICAT tariff. Skipped for Stornorechnungen (`ist_storno=true`).	`Dispute`
5	Tariff found — a PRICAT tariff record exists for the sender GLN	`Warn` (auto-accept)
6	MMM settlement price — for PIDs 31002/31005/31007/31008: Mehr-/Mindermengen prices match MMMA store	`Warn` or `Dispute`

Stornierung handling (`ist_storno = true`)

When ist_storno = Some(true), stage 4 (tariff check) is automatically skipped. A Stornierung carries negated amounts from the original invoice, not new tariff positions — checking them against PRICAT would always produce false TariffDeviation disputes.

Stage 0 enforces that original_rechnungsnummer is present on every Storno. Use is_stornierung(&rechnung) to test the flag before routing to check_storno().

use invoic_checker::{InvoicCheckEngine, is_stornierung, CheckConfig};
use rubo4e::current::Rechnung;

let rechnung: Rechnung = /* ... */;
if is_stornierung(&rechnung) {
    // Arithmetic-only path — no tariff check.
    let report = InvoicCheckEngine::check_storno(pid, &rechnung, &CheckConfig::default());
} else {
    let report = InvoicCheckEngine::check(pid, sender_mp_id, &rechnung, &store, &config);
}

Check 1.5 — Zahlungsziel

faelligkeitsdatum (DTM+92) is validated against rechnungsdatum and the configured max_zahlungsziel_days (default: 30, per §7 Allgemeine Festlegungen V6.1d). Set max_zahlungsziel_days = 0 in CheckConfig to disable this check.

Check 4 — ToU-aware tariff matching

For time-of-use tariffs, the position text (positionsbezeichnung) is used to classify HT/NT positions against the corresponding zeitvariablePreisposition band price. Positions containing "HT", "Hochtarif", or "Haupttarif" are matched against the HT band; "NT", "Niedertarif", "Nebentarif" against NT.

Check 6 — MMM settlement price

InvoicCheckEngine::check_mmm_settlement() fetches the monthly Mehr-/Mindermengenpreis (Gas or Strom) from marktd's MMMA store and compares it against the invoice's mehr_preis / minder_preis fields.

For PID 31009 (MSB-Rechnung), use check_msb_rechnung() which applies PreisblattMessung pricing (not NNE) for checks 4 and 5.

Usage

use invoic_checker::{InvoicCheckEngine, InvoicCheckInput, CheckResult};

let engine = InvoicCheckEngine::new(tariff_repo, mmma_store);

let input = InvoicCheckInput {
    pid: 31001,
    rechnung_json: serde_json::from_str(raw_invoic)?,
    malo_id: "51238696780".to_owned(),
    ..Default::default()
};

match engine.check(&input).await? {
    CheckResult::Accept(summary) => {
        // dispatch REMADV 33001 (Zahlungsavis)
    }
    CheckResult::Dispute { check, reason } => {
        // dispatch REMADV 33002 — include check number and reason
    }
    CheckResult::Warn(summary) => {
        // log and auto-accept
    }
}

Supported PIDs

PID	Process	Billing direction
31001	NNE-Rechnung Strom	NB → LF
31002	MMM-Rechnung Strom	NB → LF
31005	Selbst ausgest. NNE-Rechnung	LF → LF
31006	Selbst ausgest. Rechnung (§22 MessZV)	LF → LF
31007	Aggreg. MMM-Rechnung Gas	NB → MGV
31008	Selbst ausgest. Aggreg. MMM-Rechnung Gas	MGV → MGV
31009	MSB-Rechnung	MSB → LF

`FindingKind` variants

Variant	Stage	Dispute?	Meaning
`StorniertWithoutReference`	0	✓	`ist_storno=true` but `original_rechnungsnummer` missing
`PeriodInvalid`	1	✓	Billing period start ≥ end
`ZahlungszielInvalid`	1.5	✓	`faelligkeitsdatum` before `rechnungsdatum`
`ZahlungszielExceeded`	1.5	✗	Payment term exceeds `max_zahlungsziel_days`
`ArithmeticError`	2	✓	Line `qty × price ≠ net`
`TotalMismatch`	3	✗	Σ line nets ≠ `gesamtnetto`
`TariffDeviation`	4	✓	Unit price deviates from PRICAT
`TariffNotFound`	5	config	No PRICAT tariff for sender GLN

ERC codes

Code	Meaning
`Z30`	Rechnungsposition arithmetic error
`Z31`	Document total mismatch
`Z32`	Tariff price deviation above tolerance
`Z33`	Tariff not found
`Z34`	Invalid billing period
`Z35`	MMM settlement price mismatch
`Z36`	Stornorechnung missing original reference
`Z37`	Zahlungsziel exceeds maximum payment term

Regulatory basis

BK6-24-174 — INVOIC AHB Strom (NNE/MSB-Rechnung, PIDs 31001/31002/31005/31006/31009)
BK7-24-01-009 — INVOIC AHB Gas (GeLi Gas PID 31011)
BK7-24-01-008 — INVOIC AHB Gas (GaBi Gas PIDs 31007/31008)
BK7 billing — WiM Gas PIDs 31003/31004
§7 Allgemeine Festlegungen V6.1d — Zahlungsziel 30 days (Strom + Gas)
§22 MessZV — Pflicht zur Rechnungslegung (MSB-Rechnung receipt persistence)
REMADV AHB 1.0 — ERC-code mapping for dispute messages

invoic-checker 0.13.0