Required XML invoice fields — Peppol BIS, UBL 2.1 and SK CIUS

1. How to read field obligations

Cardinality 1..1 does not automatically mean that a field exists in every invoice. It often means that the field is mandatory inside a group that may itself be optional. This document therefore uses the following modes:

Mode	Meaning	Example
Always	The field is part of the standard invoice core.	BT-1 invoice number
Line	The field repeats and is mandatory for every InvoiceLine.	BT-126 line identifier
Condition	The field is mandatory only in a specific tax or business scenario.	BT-120 for an exemption
System	The generator or integration should supply the value, not the user.	BT-23 ProfileID
Alternative	At least one of the stated options must be present.	BT-10 or BT-13

2. Minimum core of a standard issued invoice

The following tables describe a common type 380 invoice. A credit note, corrective invoice, advance payment, reverse charge, exemption or intra-EU supply activates additional conditions.

2.1 Header and Peppol routing

Technical identifiers should be a fixed generator configuration.

Mode	BT / field	Field	XML path and rule
System	`BT-24`	Specification identifier	`/Invoice/cbc:CustomizationID` Use the profile required by the target SK/Peppol rule pack; the generator already uses the Peppol BIS Billing 3.0 value.
System	`BT-23`	Process identifier	`/Invoice/cbc:ProfileID` Peppol requires a business process. Common value: urn:fdc:peppol.eu:2017:poacc:billing:01:1.0.
Always	`BT-1`	Invoice number	`/Invoice/cbc:ID` Unique sequential invoice number.
Always	`BT-2`	Issue date	`/Invoice/cbc:IssueDate` Format YYYY-MM-DD.
Always	`BT-3`	Invoice type code	`/Invoice/cbc:InvoiceTypeCode` Use 380 for a standard invoice; the Slovak profile also supports corrective types according to its rules.
Always	`BT-5`	Invoice currency	`/Invoice/cbc:DocumentCurrencyCode` ISO 4217, typically EUR.
Alternative	`BT-10 / BT-13`	Buyer reference or purchase order	`/Invoice/cbc:BuyerReference or /Invoice/cac:OrderReference/cbc:ID` Peppol rule R003 requires at least one of these references.
Condition	`BT-9 / BT-20`	Due date or payment terms	`/Invoice/cbc:DueDate or /Invoice/cac:PaymentTerms/cbc:Note` If payable amount BT-115 is greater than zero, at least one option must be present.
Condition	`BT-7`	VAT point date	`/Invoice/cbc:TaxPointDate` State it when known and different from the issue date.

2.2 Seller

Do not mix Slovak identifiers: IČO, IČ DPH and DIČ/EndpointID belong to different XML fields.

Mode	BT / field	Field	XML path and rule
Always	`BT-27`	Seller name	`/Invoice/cac:AccountingSupplierParty/cac:Party/cac:PartyLegalEntity/cbc:RegistrationName` Full legal name.
Always	`BT-34`	Seller electronic address	`/Invoice/cac:AccountingSupplierParty/cac:Party/cbc:EndpointID` For Slovak scheme 0245 use the ten-digit DIČ without the SK prefix.
System	`BT-34-1`	Electronic address scheme	`.../cbc:EndpointID/@schemeID` For a Slovak DIČ use schemeID="0245".
Always	`BT-35`	Street and number	`.../cac:PostalAddress/cbc:StreetName` Mandatory element of a Slovak invoice.
Always	`BT-37`	City	`.../cac:PostalAddress/cbc:CityName` Mandatory element of a Slovak invoice.
Always	`BT-38`	Postcode	`.../cac:PostalAddress/cbc:PostalZone` Mandatory element of a Slovak invoice.
Always	`BT-40`	Country code	`.../cac:PostalAddress/cac:Country/cbc:IdentificationCode` ISO 3166-1 alpha-2, for example SK.
Condition	`BT-30`	Seller company number (IČO)	`.../cac:PartyLegalEntity/cbc:CompanyID` State it if assigned; use schemeID="0158" for IČO.
Condition	`BT-31`	Seller VAT identifier (IČ DPH)	`.../cac:PartyTaxScheme/cbc:CompanyID` State it for a VAT-registered seller or when the VAT category requires it.
Condition	`BT-33`	Legal form and register	`.../cac:PartyLegalEntity/cbc:CompanyLegalForm` According to Section 3a of the Slovak Commercial Code where applicable.

2.3 Buyer

The same separation of IČO, IČ DPH and Peppol EndpointID applies to a Slovak buyer.

Mode	BT / field	Field	XML path and rule
Always	`BT-44`	Buyer name	`/Invoice/cac:AccountingCustomerParty/cac:Party/cac:PartyLegalEntity/cbc:RegistrationName` Full legal name or personal name.
Always	`BT-49`	Buyer electronic address	`/Invoice/cac:AccountingCustomerParty/cac:Party/cbc:EndpointID` Peppol routing address; for scheme 0245 use the ten-digit DIČ without SK.
System	`BT-49-1`	Electronic address scheme	`.../cbc:EndpointID/@schemeID` For a Slovak DIČ use schemeID="0245".
Always	`BT-50`	Street and number	`.../cac:PostalAddress/cbc:StreetName` Mandatory element of a Slovak invoice.
Always	`BT-52`	City	`.../cac:PostalAddress/cbc:CityName` Mandatory element of a Slovak invoice.
Always	`BT-53`	Postcode	`.../cac:PostalAddress/cbc:PostalZone` Mandatory element of a Slovak invoice.
Always	`BT-55`	Country code	`.../cac:PostalAddress/cac:Country/cbc:IdentificationCode` ISO 3166-1 alpha-2.
Condition	`BT-47`	Buyer company number (IČO)	`.../cac:PartyLegalEntity/cbc:CompanyID` State it if assigned; schemeID="0158".
Condition	`BT-48`	Buyer VAT identifier (IČ DPH)	`.../cac:PartyTaxScheme/cbc:CompanyID` State it if assigned or required by the VAT treatment.

2.4 Payment

For an ordinary bank transfer, keep all three principal fields in the ERP data model.

Mode	BT / field	Field	XML path and rule
Condition	`BT-81`	Payment means code	`/Invoice/cac:PaymentMeans/cbc:PaymentMeansCode` Required when payment instructions are supplied. Code 30 is typically used for a bank transfer.
Condition	`BT-83`	Payment reference	`/Invoice/cac:PaymentMeans/cbc:PaymentID` Variable symbol or another payment reference.
Condition	`BT-84`	IBAN / account identifier	`/Invoice/cac:PaymentMeans/cac:PayeeFinancialAccount/cbc:ID` Mandatory for a transfer when the bank account group is used.
Condition	`BT-86`	BIC	`/Invoice/cac:PaymentMeans/cac:PayeeFinancialAccount/cac:FinancialInstitutionBranch/cbc:ID` Optional depending on the payment scenario and bank.

2.5 Every invoice line

These fields repeat for every cac:InvoiceLine element.

Mode	BT / field	Field	XML path and rule
Line	`BT-126`	Line identifier	`/Invoice/cac:InvoiceLine/cbc:ID` Unique within the invoice.
Line	`BT-129`	Invoiced quantity	`.../cbc:InvoicedQuantity` Numeric value; the Slovak FA allows at most four decimal places.
Line	`BT-130`	Unit of measure code	`.../cbc:InvoicedQuantity/@unitCode` UN/ECE Rec20/21, for example C62.
Line	`BT-131`	Invoice line net amount	`.../cbc:LineExtensionAmount` Excluding VAT, after line allowances and charges.
Line	`BT-146`	Item net price	`.../cac:Price/cbc:PriceAmount` Price per unit excluding VAT after discount.
Line	`BT-153`	Item name	`.../cac:Item/cbc:Name` Type of goods or services.
Line	`BT-151`	Item VAT category	`.../cac:Item/cac:ClassifiedTaxCategory/cbc:ID` For example S, Z, E, AE, IC, G or O depending on the scenario.
Condition	`BT-152`	Item VAT rate	`.../cac:Item/cac:ClassifiedTaxCategory/cbc:Percent` Greater than zero for a standard rate, zero for certain 0% treatments and omitted for O.
System	`atribút / attribute`	Currency of amount fields	`.../cbc:*Amount/@currencyID` Must match BT-5, typically EUR.

2.6 Totals and VAT breakdown

Totals must reconcile mathematically with lines, allowances, charges, paid amounts and rounding.

Mode	BT / field	Field	XML path and rule
Always	`BT-106`	Sum of invoice line net amounts	`/Invoice/cac:LegalMonetaryTotal/cbc:LineExtensionAmount` Sum of all BT-131 values.
Condition	`BT-107`	Sum of document-level allowances	`.../cbc:AllowanceTotalAmount` State it when document-level allowances exist.
Condition	`BT-108`	Sum of document-level charges	`.../cbc:ChargeTotalAmount` State it when document-level charges exist.
Always	`BT-109`	Invoice total excluding VAT	`.../cbc:TaxExclusiveAmount` BT-106 minus BT-107 plus BT-108.
Always	`BT-110`	Invoice total VAT amount	`/Invoice/cac:TaxTotal/cbc:TaxAmount` Sum of VAT amounts from all BT-117 breakdowns.
Always	`BT-112`	Invoice total including VAT	`.../cbc:TaxInclusiveAmount` BT-109 plus BT-110.
Condition	`BT-113`	Paid amount	`.../cbc:PrepaidAmount` When an advance or another paid amount is deducted.
Condition	`BT-114`	Rounding amount	`.../cbc:PayableRoundingAmount` When rounding of the payable amount is used.
Always	`BT-115`	Amount due for payment	`.../cbc:PayableAmount` BT-112 minus BT-113 plus BT-114.
Always	`BT-116`	VAT category taxable amount	`/Invoice/cac:TaxTotal/cac:TaxSubtotal/cbc:TaxableAmount` One breakdown for every category and rate combination.
Always	`BT-117`	VAT category tax amount	`.../cac:TaxSubtotal/cbc:TaxAmount` Usually zero for an exemption or reverse charge.
Always	`BT-118`	VAT category code	`.../cac:TaxSubtotal/cac:TaxCategory/cbc:ID` Must match the categories used on invoice lines.
Condition	`BT-119`	VAT category rate	`.../cac:TaxSubtotal/cac:TaxCategory/cbc:Percent` Required except when the invoice is outside the scope of VAT.
Condition	`BT-120 / BT-121`	Exemption reason or code	`.../cac:TaxCategory/cbc:TaxExemptionReason or TaxExemptionReasonCode` Mandatory for exemptions, reverse charge and other 0% treatments as required by the rules.

3. Fields that become mandatory depending on the scenario

3.1 Business and tax triggers

These are the most frequent business and tax scenarios that change the minimum XML scope.

Mode	BT / field	Field	XML path and rule
Condition	`BT-6 + BT-111`	VAT accounting currency	`/Invoice/cbc:TaxCurrencyCode + second cac:TaxTotal/cbc:TaxAmount` When the VAT accounting currency differs from the invoice currency.
Condition	`BT-25 / BT-26`	Reference to the preceding invoice	`/Invoice/cac:BillingReference/cac:InvoiceDocumentReference/...` For a corrective document, credit note or debit note.
Condition	`BT-59`	Payee name	`/Invoice/cac:PayeeParty/cac:PartyName/cbc:Name` When the payee differs from the seller.
Condition	`BT-62 – BT-69`	Seller tax representative	`/Invoice/cac:TaxRepresentativeParty/...` When a foreign seller is represented by a tax representative; name, VAT ID and country are mandatory, with the Slovak address required by the source.
Condition	`BT-72 / BG-14`	Delivery date or invoicing period	`/Invoice/cac:Delivery/cbc:ActualDeliveryDate or /Invoice/cac:InvoicePeriod` Especially for intra-EU supplies, metered services or period invoicing.
Condition	`BT-75 – BT-80`	Deliver-to address	`/Invoice/cac:Delivery/cac:DeliveryLocation/cac:Address/...` When a delivery location is stated; the country code is mandatory within the group.
Condition	`BT-92 – BT-98`	Document-level allowance	`/Invoice/cac:AllowanceCharge[cbc:ChargeIndicator='false']/...` If an allowance exists: amount, VAT category and reason or reason code.
Condition	`BT-99 – BT-105`	Document-level charge	`/Invoice/cac:AllowanceCharge[cbc:ChargeIndicator='true']/...` If a charge exists: amount, VAT category and reason or reason code.
Condition	`BT-136 – BT-140`	Invoice line allowance	`/Invoice/cac:InvoiceLine/cac:AllowanceCharge[cbc:ChargeIndicator='false']/...` When the discount was not applied directly in the unit price.
Condition	`BT-141 – BT-145`	Invoice line charge	`/Invoice/cac:InvoiceLine/cac:AllowanceCharge[cbc:ChargeIndicator='true']/...` When a charge is applied to a specific invoice line.
Condition	`BT-122 – BT-125`	Supporting document / attachment	`/Invoice/cac:AdditionalDocumentReference/...` When a reference or binary attachment is added; the reference is mandatory and an embedded file needs a MIME type and filename.
Condition	`BT-157 / BT-158`	Item identifier scheme	`.../cac:Item/.../@schemeID` Mandatory only when a standard or classification identifier is provided.
Condition	`BT-160 / BT-161`	Item attribute	`.../cac:Item/cac:AdditionalItemProperty/...` If an item property is used, it must have both a name and a value.

3.2 Most common VAT treatments

Scenario	Key codes	Additional checks
Standard rate	BT-151/118 = S	Seller BT-31; BT-152 and BT-119 > 0; VAT is calculated from the taxable amount.
Reverse charge	AE	Seller and buyer identifiers, zero rate, zero VAT and BT-120 or BT-121 with a reverse-charge reason.
VAT exemption	E	Zero VAT and a mandatory exemption reason or code.
Intra-EU supply	IC	VAT IDs of both parties, delivery date or period, destination country and exemption reason.
Export	G	Zero VAT and the relevant reason or code; check delivery data.
Outside scope of VAT / non-taxable person	O	Exactly one O breakdown; omit VAT IDs and rates where rules prohibit them; the reason must be consistent.

4. Slovak identifiers: what belongs where

Slovak identifiers have different meanings and must not be mapped into one universal field.

Identifier	Seller	Buyer	UBL path / scheme
IČO — Slovak company number	BT-30	BT-47	cac:PartyLegalEntity/cbc:CompanyID, schemeID="0158"
IČ DPH — Slovak VAT ID	BT-31	BT-48	cac:PartyTaxScheme/cbc:CompanyID, value SK + 10 digits
DIČ as the Peppol address	BT-34	BT-49	cbc:EndpointID, schemeID="0245", 10 digits without the SK prefix

Warning: the Slovak company number (IČO) is not a Peppol EndpointID. Do not add the UBL element cbc:UUID either. Any transport or internal UUID is technical metadata outside the business content of the invoice.

5. Shortened XML skeleton of a standard invoice

The skeleton is deliberately shortened. It shows where the principal data belongs; a production document must pass XSD, EN 16931, Peppol and SK CIUS rules.

UBL 2.1 · shortened skeleton

<Invoice xmlns="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2"
  xmlns:cbc="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2"
  xmlns:cac="urn:oasis:names:specification:ubl:schema:xsd:CommonAggregateComponents-2">
  <cbc:CustomizationID>urn:cen.eu:en16931:2017#compliant#urn:fdc:peppol.eu:2017:poacc:billing:3.0</cbc:CustomizationID>
  <cbc:ProfileID>urn:fdc:peppol.eu:2017:poacc:billing:01:1.0</cbc:ProfileID>
  <cbc:ID>{{invoice_number}}</cbc:ID>
  <cbc:IssueDate>{{YYYY-MM-DD}}</cbc:IssueDate>
  <cbc:DueDate>{{YYYY-MM-DD}}</cbc:DueDate>
  <cbc:InvoiceTypeCode>380</cbc:InvoiceTypeCode>
  <cbc:DocumentCurrencyCode>EUR</cbc:DocumentCurrencyCode>
  <cbc:BuyerReference>{{buyer_reference}}</cbc:BuyerReference>

  <cac:AccountingSupplierParty>
    <cac:Party>
      <cbc:EndpointID schemeID="0245">{{seller_DIC_without_SK}}</cbc:EndpointID>
      <cac:PostalAddress>
        <cbc:StreetName>{{street}}</cbc:StreetName>
        <cbc:CityName>{{city}}</cbc:CityName>
        <cbc:PostalZone>{{postal_code}}</cbc:PostalZone>
        <cac:Country><cbc:IdentificationCode>SK</cbc:IdentificationCode></cac:Country>
      </cac:PostalAddress>
      <cac:PartyTaxScheme>
        <cbc:CompanyID>{{seller_IC_DPH}}</cbc:CompanyID>
        <cac:TaxScheme><cbc:ID>VAT</cbc:ID></cac:TaxScheme>
      </cac:PartyTaxScheme>
      <cac:PartyLegalEntity>
        <cbc:RegistrationName>{{seller_name}}</cbc:RegistrationName>
        <cbc:CompanyID schemeID="0158">{{seller_ICO}}</cbc:CompanyID>
      </cac:PartyLegalEntity>
    </cac:Party>
  </cac:AccountingSupplierParty>

  <cac:AccountingCustomerParty>
    <cac:Party>
      <cbc:EndpointID schemeID="0245">{{buyer_DIC_without_SK}}</cbc:EndpointID>
      <!-- address, VAT ID and PartyLegalEntity follow the same pattern as for the supplier -->
    </cac:Party>
  </cac:AccountingCustomerParty>

  <cac:PaymentMeans>
    <cbc:PaymentMeansCode>30</cbc:PaymentMeansCode>
    <cbc:PaymentID>{{payment_reference}}</cbc:PaymentID>
    <cac:PayeeFinancialAccount><cbc:ID>{{IBAN}}</cbc:ID></cac:PayeeFinancialAccount>
  </cac:PaymentMeans>

  <cac:TaxTotal>
    <cbc:TaxAmount currencyID="EUR">{{VAT_total}}</cbc:TaxAmount>
    <cac:TaxSubtotal>
      <cbc:TaxableAmount currencyID="EUR">{{tax_base}}</cbc:TaxableAmount>
      <cbc:TaxAmount currencyID="EUR">{{VAT_amount}}</cbc:TaxAmount>
      <cac:TaxCategory>
        <cbc:ID>S</cbc:ID>
        <cbc:Percent>23</cbc:Percent>
        <cac:TaxScheme><cbc:ID>VAT</cbc:ID></cac:TaxScheme>
      </cac:TaxCategory>
    </cac:TaxSubtotal>
  </cac:TaxTotal>

  <cac:LegalMonetaryTotal>
    <cbc:LineExtensionAmount currencyID="EUR">{{BT-106}}</cbc:LineExtensionAmount>
    <cbc:TaxExclusiveAmount currencyID="EUR">{{BT-109}}</cbc:TaxExclusiveAmount>
    <cbc:TaxInclusiveAmount currencyID="EUR">{{BT-112}}</cbc:TaxInclusiveAmount>
    <cbc:PayableAmount currencyID="EUR">{{BT-115}}</cbc:PayableAmount>
  </cac:LegalMonetaryTotal>

  <cac:InvoiceLine>
    <cbc:ID>1</cbc:ID>
    <cbc:InvoicedQuantity unitCode="C62">{{quantity}}</cbc:InvoicedQuantity>
    <cbc:LineExtensionAmount currencyID="EUR">{{line_net}}</cbc:LineExtensionAmount>
    <cac:Item>
      <cbc:Name>{{item_name}}</cbc:Name>
      <cac:ClassifiedTaxCategory>
        <cbc:ID>S</cbc:ID><cbc:Percent>23</cbc:Percent>
        <cac:TaxScheme><cbc:ID>VAT</cbc:ID></cac:TaxScheme>
      </cac:ClassifiedTaxCategory>
    </cac:Item>
    <cac:Price><cbc:PriceAmount currencyID="EUR">{{unit_net_price}}</cbc:PriceAmount></cac:Price>
  </cac:InvoiceLine>
</Invoice>

6. Fields marked by the Financial Administration as conditionally required

The following list comes from the v1.10 column “Mandatory invoice requirement under Slovak legislation”. The trigger is summarised for implementation; detailed validator rules always take precedence.

BT	Field	Practical trigger	Source note
BT-6	VAT accounting currency code	When the VAT accounting currency differs from the invoice currency.	According to the rule and business-group context.
BT-7	VAT point date	When known and different from the issue date.	§ 74 ods. 1 písm. d)
BT-30	Seller legal registration identifier	If the seller has been assigned an IČO.	Required if the entity was assigned an IČO.
BT-30-1	Scheme identifier	When BT-30 is present; identifies its scheme.	Required if the entity was assigned an IČO.
BT-31	Seller VAT identifier	If a VAT ID was assigned or the VAT treatment requires it.	Required if a VAT identifier was assigned.
BT-33	Additional seller legal information — legal form	When legal-form or register information applies to the business.	Section 3a of the Slovak Commercial Code: a business states the legally required registration information on business documents.
BT-47	Buyer legal registration identifier	If the buyer has been assigned an IČO.	Required if the entity was assigned an IČO.
BT-47-1	Scheme identifier	When BT-47 is present; identifies its scheme.	Required if the entity was assigned an IČO.
BT-48	Buyer VAT identifier	If a VAT ID was assigned or the VAT treatment requires it.	Required if a VAT identifier was assigned.
BT-64	Tax representative address line 1	When a tax representative participates in the transaction.	Tax representative address under Slovak legislative requirements.
BT-66	Tax representative city	When a tax representative participates in the transaction.	Tax representative address under Slovak legislative requirements.
BT-67	Tax representative postcode	When a tax representative participates in the transaction.	Tax representative address under Slovak legislative requirements.
BT-119	VAT category rate	When the VAT category requires a rate, except where the invoice is outside the scope of VAT.	§ 74 ods. 1 písm. h)
BT-120	VAT exemption reason text	For an exemption, reverse charge or another treatment requiring a textual reason.	§ 74 ods. 1 písm. h)
BT-148	Item gross price	When a gross price is used and the discounted net price is derived from it.	If the net price is not provided directly, the gross price and discount are required.

7. Delivery checklist for the client or ERP vendor

Check	Acceptance criterion	Owner
Identifiers	IČO, IČ DPH and DIČ/EndpointID are three separate fields mapped to the correct BTs.	ERP master data
Header	The generator supplies BT-23, BT-24, BT-1, BT-2, BT-3, BT-5 and BT-10 or BT-13.	ERP / integration
Parties	Supplier and customer both have an EndpointID with schemeID and a complete postal address.	Master data
Lines	Every line contains BT-126, 129, 130, 131, 146, 151, 153 and the correct rate for the treatment.	Invoicing
VAT and totals	BT-106/109/110/112/115 and every VAT breakdown reconcile mathematically with the lines.	ERP / accounting
Conditions	Reverse charge, exemptions, intra-EU supplies, allowances, charges and attachments activate the relevant fields.	Tax / integration
Validation	XML passes XSD, EN 16931, Peppol BIS and SK CIUS; production sending is fail-closed.	Integration

8. Sources and document boundaries

Primary local source

2026.06.25_Peppol_Bis3_v1_10.xlsx

Slovak Financial Administration

financnasprava.sk · eFaktúra · InfoSW

Peppol BIS Billing 3.0

docs.peppol.eu/poacc/billing/3.0/

Internal alignment

peppol-issued-invoice-atomic-bt-map.md · efaktura-bt-human-fields.md · VerifyEU production validation rules

This document is an implementation aid, not a legal opinion. After any change in legislation or the rule pack, re-check the current source version and validation.

Required fields of an issued XML invoice