Participant ID 9950 or 0245
Short answer
Slovak tax entities must have under PASR (Peppol The Authority Specific Requirements scheme 0245:tax identification number, not the older scheme 9950. If the company has Peppol Directory identifier beginning with 9950, will have to choose a delivery service provider who will enter it in the Slovak Central SMP with the new identifier 0245.
Current Slovak Scheme
Mandatory identifier for Slovak tax entities according to PASR value is tax identification number without a EN prefix.
Older/other scheme
The company can have it registered historically, but for Slovak e-invoice the mode is not determinative.
How to switch to 0245
Choose a delivery service provider who will sign you into the Slovak Central SMP with the identifier 0245.
Two sets of documents received
If a company has a different set of accepted documents in the SMP for each Participant ID, this needs to be addressed individually with the provider.
Conclusion
Financial Administration of the Slovak Republic, FAQ 9/VAT/2025/IM k e-invoice, July 2026 update
Not legal advice. Machine-translated answer, not yet manually reviewed. For the exact wording, see the Slovak original.