diff --git a/addons/hr_timesheet/models/hr_timesheet.py b/addons/hr_timesheet/models/hr_timesheet.py
index c2f511440bf..e7d9ff2e348 100644
--- a/addons/hr_timesheet/models/hr_timesheet.py
+++ b/addons/hr_timesheet/models/hr_timesheet.py
@@ -155,7 +155,7 @@ class AccountAnalyticLine(models.Model):
             vals['account_id'] = project.analytic_account_id.id
             vals['company_id'] = project.analytic_account_id.company_id.id or project.company_id.id
             if not project.analytic_account_id.active:
-                raise UserError(_('The project you are timesheeting on is not linked to an active analytic account. Set one on the project configuration.'))
+                raise UserError(_('You cannot add timesheets to a project linked to an inactive analytic account.'))
         # employee implies user
         if vals.get('employee_id') and not vals.get('user_id'):
             employee = self.env['hr.employee'].browse(vals['employee_id'])
diff --git a/addons/hr_timesheet/models/project.py b/addons/hr_timesheet/models/project.py
index 5b894822fc1..3f5402a806a 100644
--- a/addons/hr_timesheet/models/project.py
+++ b/addons/hr_timesheet/models/project.py
@@ -40,7 +40,7 @@ class Project(models.Model):
     def _check_allow_timesheet(self):
         for project in self:
             if project.allow_timesheets and not project.analytic_account_id:
-                raise ValidationError(_('To allow timesheet, your project %s should have an analytic account set.', project.name))
+                raise ValidationError(_('You cannot use timesheets without an analytic account.'))
 
     @api.depends('timesheet_ids')
     def _compute_total_timesheet_time(self):
diff --git a/addons/project_timesheet_holidays/models/account_analytic.py b/addons/project_timesheet_holidays/models/account_analytic.py
index 833330ad7c0..dab13a7c470 100644
--- a/addons/project_timesheet_holidays/models/account_analytic.py
+++ b/addons/project_timesheet_holidays/models/account_analytic.py
@@ -13,4 +13,4 @@ class AccountAnalyticLine(models.Model):
     @api.ondelete(at_uninstall=False)
     def _unlink_except_linked_leave(self):
         if any(line.holiday_id for line in self):
-            raise UserError(_('You cannot delete timesheet lines attached to a leaves. Please cancel the leaves instead.'))
+            raise UserError(_('You cannot delete timesheets linked to time off. Please, cancel the time off instead.'))
diff --git a/addons/project_timesheet_holidays/models/hr_holidays.py b/addons/project_timesheet_holidays/models/hr_holidays.py
index d7128f4234f..634736b2ba6 100644
--- a/addons/project_timesheet_holidays/models/hr_holidays.py
+++ b/addons/project_timesheet_holidays/models/hr_holidays.py
@@ -21,7 +21,7 @@ class HolidaysType(models.Model):
         help="If checked, when validating a time off, timesheet will be generated in the Vacation Project of the company.")
     timesheet_project_id = fields.Many2one('project.project', string="Project", default=_default_project_id, domain="[('company_id', '=', company_id)]", help="The project will contain the timesheet generated when a time off is validated.")
     timesheet_task_id = fields.Many2one(
-        'project.task', string="Task for timesheet", compute='_compute_timesheet_task_id',
+        'project.task', string="Task", compute='_compute_timesheet_task_id',
         store=True, readonly=False, default=_default_task_id,
         domain="[('project_id', '=', timesheet_project_id),"
                 "('company_id', '=', company_id)]")
diff --git a/addons/project_timesheet_holidays/views/hr_holidays_views.xml b/addons/project_timesheet_holidays/views/hr_holidays_views.xml
index 845b3e11905..e92d2955df7 100644
--- a/addons/project_timesheet_holidays/views/hr_holidays_views.xml
+++ b/addons/project_timesheet_holidays/views/hr_holidays_views.xml
@@ -7,9 +7,9 @@
         <field name="inherit_id" ref="hr_holidays.edit_holiday_status_form"/>
         <field name="arch" type="xml">
             <xpath expr="//group[@name='calendar']" position="after">
-                <group name="timesheet" string="Timesheet" groups="base.group_no_one">
+                <group name="timesheet" string="Timesheets" groups="base.group_no_one">
                     <field name="timesheet_project_id" context="{'active_test': False}"/>
-                    <field name="timesheet_task_id" context="{'active_test': False}"/>
+                    <field name="timesheet_task_id" context="{'active_test': False}" attrs="{'required': [('timesheet_project_id', '!=', False)]}"/>
                     <field name="timesheet_generate" invisible="1"/>
                 </group>
 
diff --git a/addons/sale_timesheet/models/account.py b/addons/sale_timesheet/models/account.py
index 56d906cf5d7..ea71965757b 100644
--- a/addons/sale_timesheet/models/account.py
+++ b/addons/sale_timesheet/models/account.py
@@ -64,7 +64,7 @@ class AccountAnalyticLine(models.Model):
     def _check_can_write(self, values):
         if self.sudo().filtered(lambda aal: aal.so_line.product_id.invoice_policy == "delivery") and self.filtered(lambda t: t.timesheet_invoice_id and t.timesheet_invoice_id.state != 'cancel'):
             if any(field_name in values for field_name in ['unit_amount', 'employee_id', 'project_id', 'task_id', 'so_line', 'amount', 'date']):
-                raise UserError(_('You can not modify already invoiced timesheets (linked to a Sales order items invoiced on Time and material).'))
+                raise UserError(_('You cannot modify timesheets that are already invoiced.'))
 
     @api.model
     def _timesheet_preprocess(self, values):
diff --git a/addons/sale_timesheet/models/product.py b/addons/sale_timesheet/models/product.py
index 63183f0a3b0..6bece37f0e7 100644
--- a/addons/sale_timesheet/models/product.py
+++ b/addons/sale_timesheet/models/product.py
@@ -93,7 +93,7 @@ class ProductTemplate(models.Model):
     def _unlink_except_master_data(self):
         time_product = self.env.ref('sale_timesheet.time_product')
         if time_product.product_tmpl_id in self:
-            raise ValidationError(_('The %s product is required by the Timesheet app and cannot be archived/deleted.') % time_product.name)
+            raise ValidationError(_('The %s product is required by the Timesheets app and cannot be archived nor deleted.') % time_product.name)
 
     def write(self, vals):
         # timesheet product can't be archived
@@ -101,7 +101,7 @@ class ProductTemplate(models.Model):
         if not test_mode and 'active' in vals and not vals['active']:
             time_product = self.env.ref('sale_timesheet.time_product')
             if time_product.product_tmpl_id in self:
-                raise ValidationError(_('The %s product is required by the Timesheet app and cannot be archived/deleted.') % time_product.name)
+                raise ValidationError(_('The %s product is required by the Timesheets app and cannot be archived nor deleted.') % time_product.name)
         return super(ProductTemplate, self).write(vals)
 
 
@@ -126,7 +126,7 @@ class ProductProduct(models.Model):
     def _unlink_except_master_data(self):
         time_product = self.env.ref('sale_timesheet.time_product')
         if time_product in self:
-            raise ValidationError(_('The %s product is required by the Timesheet app and cannot be archived/deleted.') % time_product.name)
+            raise ValidationError(_('The %s product is required by the Timesheets app and cannot be archived nor deleted.') % time_product.name)
 
     def write(self, vals):
         # timesheet product can't be archived
@@ -134,5 +134,5 @@ class ProductProduct(models.Model):
         if not test_mode and 'active' in vals and not vals['active']:
             time_product = self.env.ref('sale_timesheet.time_product')
             if time_product in self:
-                raise ValidationError(_('The %s product is required by the Timesheet app and cannot be archived/deleted.') % time_product.name)
+                raise ValidationError(_('The %s product is required by the Timesheets app and cannot be archived nor deleted.') % time_product.name)
         return super(ProductProduct, self).write(vals)
diff --git a/addons/sale_timesheet/models/project.py b/addons/sale_timesheet/models/project.py
index 29d071ebd78..b05f57172f8 100644
--- a/addons/sale_timesheet/models/project.py
+++ b/addons/sale_timesheet/models/project.py
@@ -88,7 +88,7 @@ class Project(models.Model):
         if operator not in ('=', '!='):
             raise UserError(_('Operation not supported'))
         if not ((isinstance(value, bool) and value is False) or (isinstance(value, str) and value in ('task_rate', 'fixed_rate', 'employee_rate'))):
-            return UserError(_('Value does not exist in the pricing type'))
+            raise UserError(_('Value does not exist in the pricing type'))
         if value is False:
             return [('allow_billable', operator, value)]
 
@@ -167,9 +167,9 @@ class Project(models.Model):
     def _check_sale_line_type(self):
         for project in self.filtered(lambda project: project.sale_line_id):
             if not project.sale_line_id.is_service:
-                raise ValidationError(_("A billable project should be linked to a Sales Order Item having a Service product."))
+                raise ValidationError(_("You cannot link a billable project to a sales order item that is not a service."))
             if project.sale_line_id.is_expense:
-                raise ValidationError(_("A billable project should be linked to a Sales Order Item that does not come from an expense or a vendor bill."))
+                raise ValidationError(_("You cannot link a billable project to a sales order item that comes from an expense or a vendor bill."))
 
     def write(self, values):
         res = super(Project, self).write(values)