diff --git a/intrastat_product/models/intrastat_product_declaration.py b/intrastat_product/models/intrastat_product_declaration.py
index 36a87e8..fcbcb79 100644
--- a/intrastat_product/models/intrastat_product_declaration.py
+++ b/intrastat_product/models/intrastat_product_declaration.py
@@ -473,6 +473,8 @@ class IntrastatProductDeclaration(models.Model):
         Complete this method in the localization module
         with the country-specific logic for arrivals and dispatches.
         Cf. l10n_be_intrastat_product_declaration for an example
+        The dates are based on account.move,date in stead of invoice_date
+        to ensure consistency between intrastat and intracomm tax declaration.
         """
         start_date = date(int(self.year), int(self.month), 1)
         end_date = start_date + relativedelta(day=1, months=+1, days=-1)
diff --git a/intrastat_product/readme/ROADMAP.rst b/intrastat_product/readme/ROADMAP.rst
new file mode 100644
index 0000000..6f75021
--- /dev/null
+++ b/intrastat_product/readme/ROADMAP.rst
@@ -0,0 +1,3 @@
+The declaration is based upon the invoices of the corresponding tax declaration period.
+
+An option to generate the intrastat declaration based upon the dates of the physical movements of goods is currently not available.