diff --git a/app/assets/javascripts/controllers/admin/invoices.js.erb b/app/assets/javascripts/controllers/admin/invoices.js.erb
index cd0bd622f..33dde1fb4 100644
--- a/app/assets/javascripts/controllers/admin/invoices.js.erb
+++ b/app/assets/javascripts/controllers/admin/invoices.js.erb
@@ -676,8 +676,8 @@ Application.Controllers.controller('AvoirModalController', ['$scope', '$uibModal
 /**
  * Controller used in the modal window allowing an admin to close an accounting period
  */
-Application.Controllers.controller('ClosePeriodModalController', ['$scope', '$uibModalInstance', '$window', 'Invoice', 'AccountingPeriod', 'periods', 'lastClosingEnd','dialogs', 'growl', '_t',
-  function ($scope, $uibModalInstance, $window, Invoice, AccountingPeriod, periods, lastClosingEnd, dialogs, growl, _t) {
+Application.Controllers.controller('ClosePeriodModalController', ['$scope', '$uibModalInstance', '$window', '$sce', 'Invoice', 'AccountingPeriod', 'periods', 'lastClosingEnd','dialogs', 'growl', '_t',
+  function ($scope, $uibModalInstance, $window, $sce, Invoice, AccountingPeriod, periods, lastClosingEnd, dialogs, growl, _t) {
     const YESTERDAY = moment.utc({ h: 0, m: 0, s: 0, ms: 0 }).subtract(1, 'day').toDate();
     const LAST_CLOSING = moment.utc(lastClosingEnd.last_end_date).toDate();
     const MAX_END = moment.utc(lastClosingEnd.last_end_date).add(1, 'year').subtract(1, 'day').toDate();
@@ -734,9 +734,15 @@ Application.Controllers.controller('ClosePeriodModalController', ['$scope', '$ui
             object () {
               return {
                 title: _t('invoices.confirmation_required'),
-                msg: _t(
-                  'invoices.confirm_close_START_END',
-                  { START: moment.utc($scope.period.start_at).format('LL'), END: moment.utc($scope.period.end_at).format('LL') }
+                msg: $sce.trustAsHtml(
+                  _t(
+                    'invoices.confirm_close_START_END',
+                    { START: moment.utc($scope.period.start_at).format('LL'), END: moment.utc($scope.period.end_at).format('LL') }
+                  )
+                  + '<br/><br/><strong>'
+                  + _t('invoices.period_must_match_fiscal_year')
+                  + '</strong><br/><br/>'
+                  + _t('invoices.this_may_take_a_while')
                 )
               };
             }
diff --git a/app/models/accounting_period.rb b/app/models/accounting_period.rb
index 5178e6255..0ee4e389c 100644
--- a/app/models/accounting_period.rb
+++ b/app/models/accounting_period.rb
@@ -14,6 +14,7 @@ class AccountingPeriod < ActiveRecord::Base
 
   validates :start_at, :end_at, :closed_at, :closed_by, presence: true
   validates_with DateRangeValidator
+  validates_with DurationValidator
   validates_with PeriodOverlapValidator
   validates_with PeriodIntegrityValidator
 
diff --git a/app/validators/duration_validator.rb b/app/validators/duration_validator.rb
new file mode 100644
index 000000000..fa30e9a37
--- /dev/null
+++ b/app/validators/duration_validator.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+# Validates that the duration between start_at and end_at is between 1 day and 1 year
+class DurationValidator < ActiveModel::Validator
+  def validate(record)
+    the_end = record.end_at
+    the_start = record.start_at
+    diff = (the_end - the_start).to_i
+    return if diff.days >= 1.day && diff.days <= 1.year
+
+    record.errors[:end_at] << I18n.t('errors.messages.invalid_duration', DAYS: diff)
+  end
+end
diff --git a/config/locales/app.admin.en.yml b/config/locales/app.admin.en.yml
index 1e96f1610..c9dee138c 100644
--- a/config/locales/app.admin.en.yml
+++ b/config/locales/app.admin.en.yml
@@ -421,7 +421,9 @@ en:
           perpetual_total: "Perpetual total"
           integrity: "Integrity check"
           confirmation_required: "Confirmation required"
-          confirm_close_START_END: "Do you really want to close the accounting period between {{START}} and {{END}}? Any subsequent changes will be impossible. This operation will take some time to complete"
+          confirm_close_START_END: "Do you really want to close the accounting period between {{START}} and {{END}}? Any subsequent changes will be impossible."
+          period_must_match_fiscal_year: "A closing must occur at the end of a minimum annual period, or per financial year when it is not calendar-based."
+          this_may_take_a_while: "This operation will take some time to complete."
           period_START_END_closed_success: "The accounting period from {{START}} to {{END}} has been successfully closed"
           failed_to_close_period: "An error occurred, unable to close the accounting period"
           no_periods: "No closings for now"
diff --git a/config/locales/app.admin.es.yml b/config/locales/app.admin.es.yml
index fe4266d0e..825a1dfdb 100644
--- a/config/locales/app.admin.es.yml
+++ b/config/locales/app.admin.es.yml
@@ -421,7 +421,9 @@ es:
           perpetual_total: "Perpetual total"                                           # translation_missing
           integrity: "Verificación de integridad"
           confirmation_required: "Confirmation required"                               # translation_missing
-          confirm_close_START_END: "Do you really want to close the accounting period between {{START}} and {{END}}? Any subsequent changes will be impossible. This operation will take some time to complete"       # translation_missing
+          confirm_close_START_END: "Do you really want to close the accounting period between {{START}} and {{END}}? Any subsequent changes will be impossible."       # translation_missing
+          period_must_match_fiscal_year: "A closing must occur at the end of a minimum annual period, or per financial year when it is not calendar-based."            # translation_missing
+          this_may_take_a_while: "This operation will take some time to complete."       # translation_missing
           period_START_END_closed_success: "The accounting period from {{START}} to {{END}} has been successfully closed"        # translation_missing
           failed_to_close_period: "An error occurred, unable to close the accounting period"                                     # translation_missing
           no_periods: "No closings for now"                                            # translation_missing
diff --git a/config/locales/app.admin.fr.yml b/config/locales/app.admin.fr.yml
index 508e1c7ba..d04470e92 100644
--- a/config/locales/app.admin.fr.yml
+++ b/config/locales/app.admin.fr.yml
@@ -421,7 +421,9 @@ fr:
           perpetual_total: "Total perpétuel"
           integrity: "Contrôle d'intégrité"
           confirmation_required: "Confirmation requise"
-          confirm_close_START_END: "Êtes-vous sur de vouloir clôturer la période comptable du {{START}} au {{END}} ? Toute modification ultérieure sera impossible. Cette opération va prendre un certain temps."
+          confirm_close_START_END: "Êtes-vous sur de vouloir clôturer la période comptable du {{START}} au {{END}} ? Toute modification ultérieure sera impossible."
+          period_must_match_fiscal_year: "Une clôture doit intervenir à l'issue d'une période au minimum annuelle, ou par exercice lorsque celui-ci n'est pas calé sur l'année civile."
+          this_may_take_a_while: "Cette opération va prendre un certain temps."
           period_START_END_closed_success: "La période comptable du {{START}} au {{END}} a bien été clôturée"
           failed_to_close_period: "Une erreur est survenue, impossible de clôturer la période comptable"
           no_periods: "Aucune clôture pour le moment"
diff --git a/config/locales/app.admin.pt.yml b/config/locales/app.admin.pt.yml
index 4d0f916a3..6291094bf 100755
--- a/config/locales/app.admin.pt.yml
+++ b/config/locales/app.admin.pt.yml
@@ -421,7 +421,9 @@ pt:
           perpetual_total: "Perpetual total"                                           # translation_missing
           integrity: "Verificação de integridade"
           confirmation_required: "Confirmation required"                               # translation_missing
-          confirm_close_START_END: "Do you really want to close the accounting period between {{START}} and {{END}}? Any subsequent changes will be impossible. This operation will take some time to complete."       # translation_missing
+          confirm_close_START_END: "Do you really want to close the accounting period between {{START}} and {{END}}? Any subsequent changes will be impossible"       # translation_missing
+          period_must_match_fiscal_year: "A closing must occur at the end of a minimum annual period, or per financial year when it is not calendar-based."           # translation_missing
+          this_may_take_a_while: "This operation will take some time to complete."       # translation_missing
           period_START_END_closed_success: "The accounting period from {{START}} to {{END}} has been successfully closed"        # translation_missing
           failed_to_close_period: "An error occurred, unable to close the accounting period"                                     # translation_missing
           no_periods: "No closings for now"                                            # translation_missing
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 0690a80e2..39ca81d2c 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -41,6 +41,7 @@ en:
       in_closed_period: "can't be within a closed accounting period"
       invalid_footprint: "invoice's checksum is invalid"
       end_before_start: "The end date can't be before the start date. Pick a date after %{START}"
+      invalid_duration: "The allowed duration must be between 1 day and 1 year. Your period is %{DAYS} days long."
 
   activemodel:
     errors:
diff --git a/config/locales/es.yml b/config/locales/es.yml
index 7b63df33d..3d5096355 100644
--- a/config/locales/es.yml
+++ b/config/locales/es.yml
@@ -41,6 +41,7 @@ es:
       in_closed_period: "can't be within a closed accounting period"                              # missing translation
       invalid_footprint: "invoice's checksum is invalid"                                          # missing translation
       end_before_start: "The end date can't be before the start date. Pick a date after %{START}" # missing translation
+      invalid_duration: "The allowed duration must be between 1 day and 1 year. Your period is %{DAYS} days long."                   # missing translation
 
   activemodel:
     errors:
diff --git a/config/locales/fr.yml b/config/locales/fr.yml
index aedcbcee7..cd6c3760a 100644
--- a/config/locales/fr.yml
+++ b/config/locales/fr.yml
@@ -41,6 +41,7 @@ fr:
       in_closed_period: "ne peut pas être dans une période comptable fermée"
       invalid_footprint: "la somme de contrôle de la facture est invalide"
       end_before_start: "La date de fin ne peut pas être antérieure à la date de début. Choisissez une date après le %{START}"
+      invalid_duration: "La durée doit être comprise entre 1 jour et 1 an. Votre période dure %{DAYS} jours."
 
   activemodel:
     errors:
diff --git a/config/locales/pt.yml b/config/locales/pt.yml
index 00ef49273..298be6c00 100755
--- a/config/locales/pt.yml
+++ b/config/locales/pt.yml
@@ -41,6 +41,7 @@ pt:
       in_closed_period: "can't be within a closed accounting period"                              # missing translation
       invalid_footprint: "invoice's checksum is invalid"                                          # missing translation
       end_before_start: "The end date can't be before the start date. Pick a date after %{START}" # missing translation
+      invalid_duration: "The allowed duration must be between 1 day and 1 year. Your period is %{DAYS} days long."                   # missing translation
 
   activemodel:
     errors:
diff --git a/test/integration/accounting_period_test.rb b/test/integration/accounting_period_test.rb
index 1c0948673..98aaf777e 100644
--- a/test/integration/accounting_period_test.rb
+++ b/test/integration/accounting_period_test.rb
@@ -68,4 +68,44 @@ class AccountingPeriodTest < ActionDispatch::IntegrationTest
     FileUtils.rm_rf(accounting_period.archive_folder)
   end
 
+  test 'admin tries to closes a too long period' do
+    start_at = '2012-01-01T00:00:00.000Z'
+    end_at = '2014-12-31T00:00:00.000Z'
+    diff = (end_at.to_date - start_at.to_date).to_i
+
+    post '/api/accounting_periods',
+         {
+           accounting_period: {
+             start_at: start_at,
+             end_at: end_at
+           }
+         }.to_json, default_headers
+
+    # Check response format & status
+    assert_equal 422, response.status, response.body
+    assert_equal Mime::JSON, response.content_type
+
+    # check the error
+    assert_match(/#{I18n.t('errors.messages.invalid_duration', DAYS: diff)}/, response.body)
+  end
+
+  test 'admin tries to closes an overlapping period' do
+    start_at = '2014-12-01T00:00:00.000Z'
+    end_at = '2015-02-27T00:00:00.000Z'
+
+    post '/api/accounting_periods',
+         {
+           accounting_period: {
+             start_at: start_at,
+             end_at: end_at
+           }
+         }.to_json, default_headers
+
+    # Check response format & status
+    assert_equal 422, response.status, response.body
+    assert_equal Mime::JSON, response.content_type
+
+    # check the error
+    assert_match(/#{I18n.t('errors.messages.cannot_overlap')}/, response.body)
+  end
 end