Header dates — StartDate, EndDate, FiscalYear, DateCreated

What AT checks

The Header block of the SAF-T file describes the period the file covers and when it was generated. AT enforces a few invariants on these dates:

Field	Constraint
`StartDate`	The first date covered by the file.
`EndDate`	Must be strictly after `StartDate`.
`FiscalYear`	Must equal the calendar year of `StartDate`.
`DateCreated`	Should be on or after `EndDate` — you can't generate a file before the period it covers ends.

Sub-rules SAFTCheck applies

header.dates.range — fires when StartDate ≥ EndDate.
header.dates.fiscal_year_mismatch — fires when FiscalYear doesn't match the year of StartDate (warning).
header.dates.created_before_end — fires when DateCreated < EndDate (warning; AT may still accept).
header.dates.future_end — fires when EndDate is in the future (warning).

Common mistakes

Year-end rollover. A January file with FiscalYear=2025 but StartDate=2026-01-01. The ERP rolled the year on one field but not the other.
Wrong period unit. Submitting a quarter when AT expects a month — or vice versa. The dates declare the unit; mismatching it against the submission window is a separate AT-side check.
DateCreated set during testing. Files exported during ERP setup sometimes carry a DateCreated in the past or future from when they were actually built.

How to fix

Check the export period selection in the ERP: most issues come from selecting the wrong start/end month.
If the dates are right and only the FiscalYear is off, edit the company's fiscal year setting in the ERP and re-export. For one-off submissions, the inline editor can patch FiscalYear directly on the validation result page.
If DateCreated is in the future or before EndDate, fix the ERP system clock and re-export — or use the inline editor for the immediate file.

The combined header.dates.range finding (StartDate vs EndDate) is not editable as a single field — fix StartDate or EndDate individually with the inline editor, or re-export.

Inline editor — patch FiscalYear / EndDate / DateCreated in place.
Walkthrough: SAF-T submission deadlines and AT rejection workflow