https://wsystem.dev/blogEU e-invoicing, Peppol and VAT validation for software buildersenMon, 19 Oct 2026 08:00:00 +0000https://wsystem.dev/slovakia-efaktura-2027-invoicing-softwarehttps://wsystem.dev/slovakia-efaktura-2027-invoicing-softwareMon, 19 Oct 2026 08:00:00 +0000Zifeng WeiFrom 1 January 2027 Slovak VAT payers send domestic B2B invoices as Peppol BIS 3 UBL through a certified provider. The fields the Financial Administration adds to EN 16931 (0245:DIČ endpoints, addresses, IČO, legal form, tax point date, VATEX), the timeline incl. the no-fines bill, the invoice UUID and a checklist.https://wsystem.dev/germany-bmf-letter-15-october-2026-e-invoicinghttps://wsystem.dev/germany-bmf-letter-15-october-2026-e-invoicingMon, 19 Oct 2026 08:00:00 +0000Zifeng WeiThe third BMF letter on mandatory B2B e-invoicing keeps every deadline but settles down payments (BT-113 and BT-22 until 30 June 2030), construction and gross-price invoices, corrections, business-rule errors and penalties. Paragraph by paragraph, with what to do in your software.https://wsystem.dev/eu-vat-validation-guidehttps://wsystem.dev/eu-vat-validation-guideSat, 17 Oct 2026 08:00:00 +0000Zifeng WeiFormats for all 27 member states plus Northern Ireland, how VIES works, when you must validate, consultation numbers as proof, and what each VIES error means.