Validation rules

Rule reference

This reference explains the EN 16931 / XRechnung validation rules behind every finding the API returns. The address you followed doesn't look like a rule id — here is the curated index.

Rule	What it checks
`BR-DE-1`	Payment instructions (BG-16) are missing. XRechnung requires them.
`BR-DE-2`	Seller contact details (BG-6) are missing. XRechnung requires a contact person or department.
`BR-DE-3`	Seller city (BT-37) is missing.
`BR-DE-4`	Seller postal code (BT-38) is missing.
`BR-DE-5`	Seller contact name (BT-41) is missing.
`BR-DE-6`	Seller contact phone number (BT-42) is missing.
`BR-DE-7`	Seller contact email (BT-43) is missing.
`BR-DE-8`	Buyer city (BT-52) is missing.
`BR-DE-9`	Buyer postal code (BT-53) is missing.
`BR-DE-10`	A deliver-to address (BG-15) is present but its city (BT-77) is missing — XRechnung requires it.
`BR-DE-11`	A deliver-to address (BG-15) is present but its post code (BT-78) is missing — XRechnung requires it.
`BR-DE-15`	Buyer reference (BT-10) is missing. XRechnung requires it; public-sector buyers in Germany use their Leitweg-ID here.
`BR-DE-16`	Seller VAT identifier (BT-31) or tax registration number (BT-32) is required.
`BR-DE-17`	This invoice type code is not recommended in XRechnung.
`BR-DE-18`	A payment-terms line starting with # is not a valid Skonto segment — XRechnung requires the exact format #SKONTO#TAGE=n#PROZENT=n.nn# (optionally #BASISBETRAG=n.nn#), one per line.
`BR-DE-23-a`	Payment means is a credit transfer (code 30/58) but no payment account (IBAN, BT-84) is given.
`BR-DE-23-b`	Payment means is a credit transfer (code 30/58), so direct-debit information (BG-19) must not be present.
`BR-DE-25-a`	Payment means is a SEPA direct debit (code 49/59) but direct-debit information (BG-19) is missing.
`BR-DE-25-b`	Payment means is a SEPA direct debit (code 49/59), so a payee account (BG-17) must not be present.
`BR-DE-26`	A corrected invoice (type_code 384) should reference the invoice it corrects (BT-25).
`BR-DE-27`	The seller contact phone number (BT-42) should contain at least three digits.
`BR-DE-30`	Direct-debit information (BG-19) is present but the creditor identifier (BT-90) is missing.
`BR-DE-31`	Direct-debit information (BG-19) is present but the debited account identifier (BT-91) is missing.
`BR-DE-22`	Two embedded attachments share the same filename — every attached document's filename must be unique within the invoice.
`BR-TMP-2`	An external document location (BT-124) must be an absolute URL with a valid scheme (announced to become an error in a future XRechnung release).
`PEPPOL-EN16931-R061`	A direct-debit payment (means code 49/59) must carry a mandate reference (BT-89).
`BR-CO-10`	The sum of line net amounts (BT-106) does not match the invoice lines.
`BR-CO-13`	Supplied totals.net does not equal the sum of line nets minus document allowances plus document charges.
`BR-CO-14`	Supplied totals.tax does not match the computed VAT breakdown.
`BR-CO-15`	Supplied totals.gross does not equal net + tax.
`BR-CO-16`	The amount due (BT-115) would be negative: paid_amount (BT-113) exceeds the invoice total with VAT (BT-112).
`BR-CO-25`	An amount is due but neither a due date (BT-9) nor payment terms (BT-20) are present.
`BR-DEC-01`	A document-level allowance amount (BT-92) has more than 2 decimal places.
`BR-DEC-02`	A document-level allowance base amount (BT-93) has more than 2 decimal places.
`BR-DEC-05`	A document-level charge amount (BT-99) has more than 2 decimal places.
`BR-DEC-06`	A document-level charge base amount (BT-100) has more than 2 decimal places.
`BR-DEC-12`	totals.net (BT-109) has more than 2 decimal places — EN 16931 allows at most 2.
`BR-DEC-13`	totals.tax (BT-110) has more than 2 decimal places — EN 16931 allows at most 2.
`BR-DEC-14`	totals.gross (BT-112) has more than 2 decimal places — EN 16931 allows at most 2.
`BR-DEC-24`	A line-level allowance amount (BT-136) has more than 2 decimal places.
`BR-DEC-25`	A line-level allowance base amount (BT-137) has more than 2 decimal places.
`BR-DEC-27`	A line-level charge amount (BT-141) has more than 2 decimal places.
`BR-DEC-28`	A line-level charge base amount (BT-142) has more than 2 decimal places.
`BR-S-02`	The invoice has standard-rated (S) lines, which require the seller VAT identifier (BT-31) or tax registration number (BT-32).
`BR-S-05`	A standard-rated (S) line must have a VAT rate greater than zero.
`BR-Z-05`	A zero-rated (Z) line must have a VAT rate of exactly 0.
`BR-E-05`	A VAT-exempt (E) line must have a VAT rate of 0.
`BR-AE-05`	A reverse-charge (AE) line must have a VAT rate of 0.
`BR-AE-02`	Reverse charge (AE) requires a seller VAT identifier (BT-31) or tax registration number (BT-32), and the buyer VAT identifier (BT-48).
`BR-27`	The item net price (BT-146) must not be negative.
`BR-E-10`	Lines use VAT category "E" (exempt) but no exemption reason (BT-120) or reason code (BT-121) is given.
`BR-AE-10`	Lines use VAT category "AE" (reverse charge) but no exemption reason (BT-120) or reason code (BT-121) is given.
`BR-IC-10`	Lines use VAT category "K" (intra-community supply) but no exemption reason (BT-120) or reason code (BT-121) is given.
`BR-G-10`	Lines use VAT category "G" (export outside the EU) but no exemption reason (BT-120) or reason code (BT-121) is given.
`BR-O-10`	Lines use VAT category "O" (not subject to VAT) but no exemption reason (BT-120) or reason code (BT-121) is given.
`BR-O-05`	A line "not subject to VAT" (O) must not carry a VAT rate.
`BR-O-11`	VAT category "O" (not subject to VAT) cannot be mixed with other VAT categories on the same invoice (BR-O-11..14).
`BR-32`	A document-level allowance needs a VAT category (BT-95); it cannot be inherited because the lines use more than one VAT category/rate.
`BR-37`	A document-level charge needs a VAT category (BT-102); it cannot be inherited because the lines use more than one VAT category/rate.
`BR-33`	A document-level allowance must state why it is granted (BT-97/BT-98).
`BR-38`	A document-level charge must state what it is for (BT-104/BT-105).
`BR-42`	A line-level allowance must state why it is granted (BT-139/BT-140).
`BR-44`	A line-level charge must state what it is for (BT-144/BT-145).
`NB-AC-MISMATCH`	An allowance/charge amount does not equal base_amount × percent / 100 — the KoSIT validator rejects this (PEPPOL-EN16931-R040).
`NB-LEITWEG-FORMAT`	buyer_reference does not look like a Leitweg-ID. German B2G platforms (ZRE/OZG-RE) reject malformed Leitweg-IDs. For B2B invoices any buyer reference is fine — ignore this warning then.
`NB-EADDR-SELLER`	Seller electronic address (BT-34) is missing — XRechnung requires one for both parties.
`NB-EADDR-BUYER`	Buyer electronic address (BT-49) is missing — XRechnung requires one for both parties.
`NB-IBAN-CHECKSUM`	The IBAN fails its checksum — this is almost certainly a typo.
`NB-VAT-RATE`	A line has neither a VAT rate nor a VAT category — the category cannot be determined.
`NB-PAYMENT-MEANS-UNSUPPORTED`	Card-payment means codes (48/54/55) need card information (BG-18) that normbill cannot express yet — KoSIT would reject the invoice (BR-DE-24-a).
`NB-VAT-ID-FORMAT`	A German VAT identifier (BT-31/BT-48) must be "DE" followed by exactly 9 digits. EN 16931 and the KoSIT validator only check the ISO country prefix, not the national length, so a German id with the wrong number of digits still passes tier 3 — normbill catches it here.
`NB-VALIDATOR-REJECT`	The official KoSIT validator rejected this document without a mappable rule finding — typically an XML schema (XSD) violation.
`BR-CO-26`	The seller carries none of: VAT identifier (BT-31), legal registration identifier (BT-30) or seller identifier (BT-29) — at least one is required so the buyer can identify the supplier. The German tax number (BT-32) alone does NOT satisfy this rule.
`BR-IC-11`	An intra-community supply (VAT category K) must state the actual delivery date (BT-72) or an invoicing period (BG-14).
`BR-IC-12`	An intra-community supply (VAT category K) must state the deliver-to country (BT-80).
`BR-29`	The invoicing period end date (BT-74) must not be earlier than its start date (BT-73).
`BR-30`	An invoice line period end date (BT-135) must not be earlier than its start date (BT-134).
`PEPPOL-EN16931-R110`	An invoice line period start date must lie within the document invoicing period.
`PEPPOL-EN16931-R111`	An invoice line period end date must lie within the document invoicing period.
`BR-IC-05`	An intra-community supply (K) line must have a VAT rate of exactly 0.
`BR-G-05`	An export (G) line must have a VAT rate of exactly 0.
`BR-CL-04`	The invoice currency code (BT-5) is not part of ISO 4217.
`BR-CL-14`	A country code in the invoice is not an ISO 3166-1 alpha-2 code.
`BR-CL-16`	The payment means code (BT-81) is not a UNTDID 4461 code.
`BR-CL-19`	An allowance reason code (BT-98 document level, BT-140 line level) is not part of the UNCL 5189 subset EN 16931 permits.
`BR-CL-20`	A charge reason code (BT-105 document level, BT-145 line level) is not a UNTDID 7161 code.
`BR-CL-22`	A VAT exemption reason code (BT-121) is not part of the VATEX code list.
`BR-CL-25`	An electronic address scheme (BT-34 seller, BT-49 buyer — the schemeID on cbc:EndpointID) is not part of the EAS code list.

Official sources

Every 422 from the API lists the rule id, the path in your request JSON, a plain-language message and a suggested fix — see the docs overview for the report format.

Rule reference

This reference explains the EN 16931 / XRechnung validation rules behind every finding the API returns. The address you followed doesn't look like a rule id — here is the curated index.

Rule

What it checks

BR-DE-1

Payment instructions (BG-16) are missing. XRechnung requires them.

BR-DE-2

Seller contact details (BG-6) are missing. XRechnung requires a contact person or department.

BR-DE-3

Seller city (BT-37) is missing.

BR-DE-4

Seller postal code (BT-38) is missing.

BR-DE-5

Seller contact name (BT-41) is missing.

BR-DE-6

Seller contact phone number (BT-42) is missing.

BR-DE-7

Seller contact email (BT-43) is missing.

BR-DE-8

Buyer city (BT-52) is missing.

BR-DE-9

Buyer postal code (BT-53) is missing.

BR-DE-10

A deliver-to address (BG-15) is present but its city (BT-77) is missing — XRechnung requires it.

BR-DE-11

A deliver-to address (BG-15) is present but its post code (BT-78) is missing — XRechnung requires it.

BR-DE-15

Buyer reference (BT-10) is missing. XRechnung requires it; public-sector buyers in Germany use their Leitweg-ID here.

BR-DE-16

Seller VAT identifier (BT-31) or tax registration number (BT-32) is required.

BR-DE-17

This invoice type code is not recommended in XRechnung.

BR-DE-18

A payment-terms line starting with # is not a valid Skonto segment — XRechnung requires the exact format #SKONTO#TAGE=n#PROZENT=n.nn# (optionally #BASISBETRAG=n.nn#), one per line.

BR-DE-23-a

Payment means is a credit transfer (code 30/58) but no payment account (IBAN, BT-84) is given.

BR-DE-23-b

Payment means is a credit transfer (code 30/58), so direct-debit information (BG-19) must not be present.

BR-DE-25-a

Payment means is a SEPA direct debit (code 49/59) but direct-debit information (BG-19) is missing.

BR-DE-25-b

Payment means is a SEPA direct debit (code 49/59), so a payee account (BG-17) must not be present.

BR-DE-26

A corrected invoice (type_code 384) should reference the invoice it corrects (BT-25).

BR-DE-27

The seller contact phone number (BT-42) should contain at least three digits.

BR-DE-30

Direct-debit information (BG-19) is present but the creditor identifier (BT-90) is missing.

BR-DE-31

Direct-debit information (BG-19) is present but the debited account identifier (BT-91) is missing.

BR-DE-22

Two embedded attachments share the same filename — every attached document's filename must be unique within the invoice.

BR-TMP-2

An external document location (BT-124) must be an absolute URL with a valid scheme (announced to become an error in a future XRechnung release).

PEPPOL-EN16931-R061

A direct-debit payment (means code 49/59) must carry a mandate reference (BT-89).

BR-CO-10

The sum of line net amounts (BT-106) does not match the invoice lines.

BR-CO-13

Supplied totals.net does not equal the sum of line nets minus document allowances plus document charges.

BR-CO-14

Supplied totals.tax does not match the computed VAT breakdown.

BR-CO-15

Supplied totals.gross does not equal net + tax.

BR-CO-16

The amount due (BT-115) would be negative: paid_amount (BT-113) exceeds the invoice total with VAT (BT-112).

BR-CO-25

An amount is due but neither a due date (BT-9) nor payment terms (BT-20) are present.

BR-DEC-01

A document-level allowance amount (BT-92) has more than 2 decimal places.

BR-DEC-02

A document-level allowance base amount (BT-93) has more than 2 decimal places.

BR-DEC-05

A document-level charge amount (BT-99) has more than 2 decimal places.

BR-DEC-06

A document-level charge base amount (BT-100) has more than 2 decimal places.

BR-DEC-12

totals.net (BT-109) has more than 2 decimal places — EN 16931 allows at most 2.

BR-DEC-13

totals.tax (BT-110) has more than 2 decimal places — EN 16931 allows at most 2.

BR-DEC-14

totals.gross (BT-112) has more than 2 decimal places — EN 16931 allows at most 2.

BR-DEC-24

A line-level allowance amount (BT-136) has more than 2 decimal places.

BR-DEC-25

A line-level allowance base amount (BT-137) has more than 2 decimal places.

BR-DEC-27

A line-level charge amount (BT-141) has more than 2 decimal places.

BR-DEC-28

A line-level charge base amount (BT-142) has more than 2 decimal places.

BR-S-02

The invoice has standard-rated (S) lines, which require the seller VAT identifier (BT-31) or tax registration number (BT-32).

BR-S-05

A standard-rated (S) line must have a VAT rate greater than zero.

BR-Z-05

A zero-rated (Z) line must have a VAT rate of exactly 0.

BR-E-05

A VAT-exempt (E) line must have a VAT rate of 0.

BR-AE-05

A reverse-charge (AE) line must have a VAT rate of 0.

BR-AE-02

Reverse charge (AE) requires a seller VAT identifier (BT-31) or tax registration number (BT-32), and the buyer VAT identifier (BT-48).

BR-27

The item net price (BT-146) must not be negative.

BR-E-10

Lines use VAT category "E" (exempt) but no exemption reason (BT-120) or reason code (BT-121) is given.

BR-AE-10

Lines use VAT category "AE" (reverse charge) but no exemption reason (BT-120) or reason code (BT-121) is given.

BR-IC-10

Lines use VAT category "K" (intra-community supply) but no exemption reason (BT-120) or reason code (BT-121) is given.

BR-G-10

Lines use VAT category "G" (export outside the EU) but no exemption reason (BT-120) or reason code (BT-121) is given.

BR-O-10

Lines use VAT category "O" (not subject to VAT) but no exemption reason (BT-120) or reason code (BT-121) is given.

BR-O-05

A line "not subject to VAT" (O) must not carry a VAT rate.

BR-O-11

VAT category "O" (not subject to VAT) cannot be mixed with other VAT categories on the same invoice (BR-O-11..14).

BR-32

A document-level allowance needs a VAT category (BT-95); it cannot be inherited because the lines use more than one VAT category/rate.

BR-37

A document-level charge needs a VAT category (BT-102); it cannot be inherited because the lines use more than one VAT category/rate.

BR-33

A document-level allowance must state why it is granted (BT-97/BT-98).

BR-38

A document-level charge must state what it is for (BT-104/BT-105).

BR-42

A line-level allowance must state why it is granted (BT-139/BT-140).

BR-44

A line-level charge must state what it is for (BT-144/BT-145).

NB-AC-MISMATCH

An allowance/charge amount does not equal base_amount × percent / 100 — the KoSIT validator rejects this (PEPPOL-EN16931-R040).

NB-LEITWEG-FORMAT

buyer_reference does not look like a Leitweg-ID. German B2G platforms (ZRE/OZG-RE) reject malformed Leitweg-IDs. For B2B invoices any buyer reference is fine — ignore this warning then.

NB-EADDR-SELLER

Seller electronic address (BT-34) is missing — XRechnung requires one for both parties.

NB-EADDR-BUYER

Buyer electronic address (BT-49) is missing — XRechnung requires one for both parties.

NB-IBAN-CHECKSUM

The IBAN fails its checksum — this is almost certainly a typo.

NB-VAT-RATE

A line has neither a VAT rate nor a VAT category — the category cannot be determined.

NB-PAYMENT-MEANS-UNSUPPORTED

Card-payment means codes (48/54/55) need card information (BG-18) that normbill cannot express yet — KoSIT would reject the invoice (BR-DE-24-a).

NB-VAT-ID-FORMAT

A German VAT identifier (BT-31/BT-48) must be "DE" followed by exactly 9 digits. EN 16931 and the KoSIT validator only check the ISO country prefix, not the national length, so a German id with the wrong number of digits still passes tier 3 — normbill catches it here.

NB-VALIDATOR-REJECT

The official KoSIT validator rejected this document without a mappable rule finding — typically an XML schema (XSD) violation.

BR-CO-26

The seller carries none of: VAT identifier (BT-31), legal registration identifier (BT-30) or seller identifier (BT-29) — at least one is required so the buyer can identify the supplier. The German tax number (BT-32) alone does NOT satisfy this rule.

BR-IC-11

An intra-community supply (VAT category K) must state the actual delivery date (BT-72) or an invoicing period (BG-14).

BR-IC-12

An intra-community supply (VAT category K) must state the deliver-to country (BT-80).

BR-29

The invoicing period end date (BT-74) must not be earlier than its start date (BT-73).

BR-30

An invoice line period end date (BT-135) must not be earlier than its start date (BT-134).

PEPPOL-EN16931-R110

An invoice line period start date must lie within the document invoicing period.

PEPPOL-EN16931-R111

An invoice line period end date must lie within the document invoicing period.

BR-IC-05

An intra-community supply (K) line must have a VAT rate of exactly 0.

BR-G-05

An export (G) line must have a VAT rate of exactly 0.

BR-CL-04

The invoice currency code (BT-5) is not part of ISO 4217.

BR-CL-14

A country code in the invoice is not an ISO 3166-1 alpha-2 code.

BR-CL-16

The payment means code (BT-81) is not a UNTDID 4461 code.

BR-CL-19

An allowance reason code (BT-98 document level, BT-140 line level) is not part of the UNCL 5189 subset EN 16931 permits.

BR-CL-20

A charge reason code (BT-105 document level, BT-145 line level) is not a UNTDID 7161 code.

BR-CL-22

A VAT exemption reason code (BT-121) is not part of the VATEX code list.

BR-CL-25

An electronic address scheme (BT-34 seller, BT-49 buyer — the schemeID on cbc:EndpointID) is not part of the EAS code list.