Spain's business-to-business e-invoicing duty does not name its deadlines as calendar dates. Royal Decree 238/2026 (25 March 2026) gives 12 months to businesses above 8 million euro of turnover and 24 months to everyone else, counted from when the technical order takes effect. That order, HAC/1028/2026, was published in the BOE on 5 October 2026 and took effect on 6 October, which is where the widely quoted 6 October 2027 and 6 October 2028 dates come from.
Two practical consequences. First, the dates are derived, so a later order or decree that moves the start moves them too. Second, larger businesses are reported to owe a readable PDF alongside the structured invoice during their first 12 months.
We could only read the BOE's search listing from this environment, not the order's full text, so the einvoice-preflight Spain page says so plainly and still tells readers to confirm with an adviser. What it does now cite is the legal chain (BOE-A-2026-20587 and BOE-A-2026-7295) so a reader can check the primary text in a minute. The free checker on that page validates an EN 16931 UBL invoice offline before it goes to a Spanish customer.