Practical resolution

How can I determine in practice whether I must issue e-invoice to a customer?

Short answer

Assess whether the customer is acting as a business or taxable person rather than as a final consumer. A company registration number or tax identification number is a practical indicator of a business relationship, but the statutory obligation must still be determined from the status of the parties and the particular supply. The absence of business identifiers will usually indicate a B2C transaction outside the mandatory e-invoice regime.

IČO or TIN of the customer

A practical launcher

The presence of an identifier indicates a B2B or B2G relationship.

No identifier

Probably B2C

A private person to whom the e-invoice does not apply.

System setup

Automatic resolution

The "I buy as a company" field when ordering will make the decision easier.

Additional condition

Supplier's own position

The obligation applies only if you are a VAT payer according to Section 4, Section 4b or Section 4c.

Detailed explanation

In practice, this usually means setting up a simple rule in your invoicing or ERP system when creating a new customer: if a customer provides a company registration number (IČO) or VAT number (DIČ) during registration or when placing an order, the system will flag them as a business customer for whom the invoice should be issued as an e-invoice (provided the other conditions are met, i.e. if you are a VAT payer under Section 4, Section 4b or Section 4c and the supply is domestic). If the customer does not provide any business identifier, they are most likely a private individual (B2C), for whom you do not issue an e-invoice. Many invoicing systems and online shops already include an optional field in their order form labelled ‘I am purchasing as a business’ or similar, which captures precisely this information at the time the order is placed — it is advisable to link this field to the decision as to whether the invoice should be processed as an e-invoice or as a standard document for a consumer.

As set out in the Act

The scope of transactions to which mandatory electronic invoicing applies (B2B and B2G, not B2C) is set out in Section 85o of Act No. 222/2004 Coll. on VAT, as amended by Act No. 385/2025 Coll. Identifying the customer by their VAT registration number or tax identification number as a business entity relates to the mandatory details of an invoice under Section 74(1) of the VAT Act and to the Peppol Authority Specific Requirements (PASR) for identifying participants in the Peppol network.

Practical examples

The customer ticks “I am purchasing as a business” in the online shop and enters their VAT registration number — the system flags the order for processing as an e-invoice.
If the customer makes a purchase without ticking the business option and without providing a company registration number, they will receive a standard invoice, not an e-invoice.
The company configures its ERP system so that new customers who have provided a VAT number or company registration number are automatically included in the e-invoicing process.

Most common mistakes

“The distinction between B2B and B2C must be made manually for each invoice without any system support.” Most invoicing and e-shop systems allow this distinction to be recorded at the time the order is created using a field for the company registration number or VAT number.
“If a customer has made a purchase as a business once, all their subsequent purchases are automatically classified as B2B without verification.” It is recommended to verify the current status for repeat customers with every transaction, as it may change.
“The presence of a company name in an order without a company registration number or VAT number is sufficient to classify the customer as a B2B customer.” A more reliable indicator is a specific company identifier, not just the name in the order text.

Conclusion

Business identifiers are a useful practical signal, but the parties’ status and the particular supply remain decisive for the legal assessment.

Legal basis

Act No. 222/2004 Coll. on VAT, Section 74(1) and Section 85o (as amended by Act No. 385/2025 Coll.)
Peppol Authority Specific Requirements (PASR) for the Slovak Republicublic

Review of questions from an earlier presentation

The presentation by the Slovak Accountants’ Centre was used solely to identify practical issues. The following conclusion has been updated in line with a subsequent FAQ from the Financial Administration and the applicable legislation; we do not treat the author’s suggestions, recommendations or incorrectly merged fragments as legal rules.

slide/page 42: What if I did not issue an electronic invoice as a taxable person because, at the time of supply of the goods, I did not have information that the customer was a person to whom I was obliged to issue an electronic invoice?

Current conclusion: The company registration number (IČO) or tax identification number (DIČ) are important indicators, but not the sole legal test. The decisive factors are the customer’s status and the specific supply. If the customer subsequently notifies you that they should have received an e-invoice, the FAQ specifies a period of 15 days from the date of notification.

Primary sources: FAQ Financial Administration of the Slovak Republic k e-invoice, July 2026; Act No. 222/2004 Coll. on VAT Effective from 1. 1. 2027. Revised 13 July 2026.