Approvals Module in Odoo 19:
Streamline Purchase, Expense & Leave Requests

Every Unapproved Purchase Order Is a Financial Risk You Haven't Measured

A procurement manager clicks "Confirm" on a $45,000 vendor order. No second pair of eyes. No budget check. No audit trail beyond a timestamp in mail.message. Three weeks later, finance discovers the department already exceeded its quarterly budget by 20% — but the goods are on a container ship. This happens more often than anyone in leadership wants to admit.

The Approvals module (approvals) in Odoo 19 Enterprise exists to close exactly this gap. It provides a configurable, multi-level approval engine that works across purchase requests, expense reports, leave requests, and any custom workflow you define. Unlike ad-hoc email chains or Slack messages that say "can you approve this?", the module creates a structured, auditable, enforceable approval process with clear ownership at every stage.

But the module ships with sensible defaults that cover about 40% of real-world needs. The other 60% — multi-level chains with conditional routing, minimum approver thresholds, delegation rules for vacations, integration with purchase and expense workflows, and portal access for external stakeholders — requires configuration that isn't obvious from the UI. This guide covers all of it.

Defining Approval Types and Categories: Purchase, Expense, Leave, and Custom

Approval types (model approval.category) are the backbone of the module. Each type defines what gets approved, who approves it, how many approvals are required, and which fields the requester must fill in. Navigate to Approvals → Configuration → Approval Types to create or modify them.

Odoo 19 ships with four pre-configured approval types after installing the sub-modules:

Field Visibility per Approval Type

Each approval type controls which fields appear on the request form. The approval.category model uses selection fields with three options for each configurable field: None (hidden), Optional (visible but not required), and Required (must be filled before submission). The key field visibility controls are:

• has_date — show/require start and end date fields
• has_period — show/require period selection
• has_quantity — show/require quantity field
• has_amount — show/require monetary amount
• has_reference — show/require external reference field
• has_partner — show/require contact (vendor/customer) selection
• has_payment_method — show/require payment method
• has_location — show/require location field
• has_product — show/require product lines

<odoo>
  <data noupdate="1">

    <!-- Purchase Request: requires vendor, products, and amount -->
    <record id="approval_category_purchase_request" model="approval.category">
      <field name="name">Purchase Request</field>
      <field name="sequence">10</field>
      <field name="description">
        Request approval before creating a purchase order.
        Required for all orders above $5,000.
      </field>
      <field name="approval_type">purchase</field>
      <field name="has_partner">required</field>
      <field name="has_product">required</field>
      <field name="has_amount">required</field>
      <field name="has_date">optional</field>
      <field name="has_reference">optional</field>
      <field name="has_quantity">required</field>
      <field name="has_location">no</field>
      <field name="has_payment_method">no</field>
      <field name="approval_minimum">2</field>
      <field name="manager_approval">approver</field>
      <field name="automated_sequence">True</field>
      <field name="company_id" ref="base.main_company"/>
    </record>

    <!-- Expense Report: requires amount, date, reference -->
    <record id="approval_category_expense_report" model="approval.category">
      <field name="name">Expense Report Approval</field>
      <field name="sequence">20</field>
      <field name="description">
        Submit expense reports for manager and finance approval.
      </field>
      <field name="has_partner">no</field>
      <field name="has_product">optional</field>
      <field name="has_amount">required</field>
      <field name="has_date">required</field>
      <field name="has_reference">required</field>
      <field name="has_quantity">no</field>
      <field name="has_location">optional</field>
      <field name="has_payment_method">required</field>
      <field name="approval_minimum">1</field>
      <field name="manager_approval">approver</field>
      <field name="company_id" ref="base.main_company"/>
    </record>

  </data>
</odoo>

Integrating Approvals with Purchase, Expense, and HR Modules

The real power of the Approvals module emerges when it's connected to Odoo's operational modules. Rather than standalone approval requests that exist in a vacuum, integration means an approved purchase request automatically creates a purchase order, an approved expense report moves directly to the accounting pipeline, and an approved leave request updates the HR calendar.

Purchase Integration (approvals_purchase)

Install approvals_purchase to bridge approvals with the Purchase module. Once active, the approval request form gains a Products tab where requesters can add product lines with quantities and expected unit prices. When the request is approved, clicking "Create Purchase Order" generates a draft purchase.order pre-filled with the vendor, product lines, and quantities from the approval.

The key fields on the purchase-linked approval request:

• product_line_ids — one2many to approval.product.line storing product, quantity, and description
• partner_id — the vendor (linked to res.partner with supplier_rank > 0)
• purchase_order_count — computed field showing how many POs were created from this approval

Expense Integration (hr_expense_approvals)

The expense bridge connects approval workflows to hr.expense.sheet. When an employee submits an expense report that exceeds a configured threshold, it automatically creates an approval request. The flow is: Employee submits expense → Approval request created → Manager approves → Expense moves to "Approved" state → Finance processes payment.

Email Notifications and Activity Scheduling

Every state transition in the approval workflow triggers an email notification through Odoo's mail.thread mixin. The module uses mail templates stored as mail.template records with the following triggers:

• Request submitted — notifies all approvers in the chain that a new request awaits their review
• Approved by one level — notifies the next approver in sequence that it's their turn
• Fully approved — notifies the requester and any followers that the request is complete
• Refused — notifies the requester with the refusal reason

Additionally, the module creates mail.activity records (the "to-do" items in the chatter) for each pending approver. This means approvals appear in the approver's Activity view across all Odoo modules — not just in the Approvals menu. An approver reviewing their daily tasks in the CRM will see the pending purchase approval right alongside their sales follow-ups.

<odoo>
  <data>

    <record id="mail_template_high_value_approval" model="mail.template">
      <field name="name">High-Value Approval Notification</field>
      <field name="model_id" ref="approvals.model_approval_request"/>
      <field name="subject">
        URGENT: Approval Required - {{ object.name }}
        ({{ object.amount }} {{ object.currency_id.symbol }})
      </field>
      <field name="email_from">
        {{ (object.request_owner_id.email_formatted) }}
      </field>
      <field name="email_to">
        {{ (object.approver_ids.filtered(
            lambda a: a.status == 'pending'
        ).mapped('user_id.email') | join(',')) }}
      </field>
      <field name="body_html" type="html">
        <div style="margin: 0; padding: 0;">
          <p>Dear Approver,</p>
          <p>
            A high-value approval request requires your attention:
          </p>
          <table style="border-collapse: collapse; width: 100%;">
            <tr>
              <td style="padding: 8px; border: 1px solid #ddd;">
                <strong>Reference</strong>
              </td>
              <td style="padding: 8px; border: 1px solid #ddd;">
                {{ object.name }}
              </td>
            </tr>
            <tr>
              <td style="padding: 8px; border: 1px solid #ddd;">
                <strong>Category</strong>
              </td>
              <td style="padding: 8px; border: 1px solid #ddd;">
                {{ object.category_id.name }}
              </td>
            </tr>
            <tr>
              <td style="padding: 8px; border: 1px solid #ddd;">
                <strong>Amount</strong>
              </td>
              <td style="padding: 8px; border: 1px solid #ddd;">
                {{ object.amount }}
                {{ object.currency_id.symbol }}
              </td>
            </tr>
            <tr>
              <td style="padding: 8px; border: 1px solid #ddd;">
                <strong>Requested By</strong>
              </td>
              <td style="padding: 8px; border: 1px solid #ddd;">
                {{ object.request_owner_id.name }}
              </td>
            </tr>
          </table>
          <p style="margin-top: 16px;">
            <a href="{{ object.get_base_url() }}/web#id={{ object.id }}&amp;model=approval.request&amp;view_type=form"
               style="padding: 10px 20px; background: #875A7B;
                      color: #fff; text-decoration: none;
                      border-radius: 4px;">
              Review &amp; Approve
            </a>
          </p>
        </div>
      </field>
    </record>

  </data>
</odoo>

Adding Custom Approval Fields and Reporting Dashboards

The built-in fields cover standard use cases, but most organizations need custom data on their approval requests. Common examples: cost center codes, project references, urgency levels, and budget line items. Odoo 19 supports two approaches for adding custom fields to approvals.

Approach 1: Studio (No-Code)

If you have Odoo Studio installed, open any approval request form and click the Studio icon (puzzle piece). You can drag and drop new fields directly onto the form. Studio creates x_ prefixed fields in the database and adds them to the approval.request model. This is fast for simple additions but creates technical debt for complex logic.

Approach 2: Custom Module (Recommended)

For production deployments, extend the approval.request model in a custom module. This keeps your customizations version-controlled, testable, and upgrade-safe.

from odoo import models, fields, api
from odoo.exceptions import ValidationError


class ApprovalRequestCustom(models.Model):
    _inherit = 'approval.request'

    # ── Custom Fields ──────────────────────────────
    cost_center_id = fields.Many2one(
        'account.analytic.account',
        string='Cost Center',
        help='Budget line to charge this request against.',
    )
    urgency = fields.Selection([
        ('low', 'Low — Within 30 days'),
        ('medium', 'Medium — Within 7 days'),
        ('high', 'High — Within 48 hours'),
        ('critical', 'Critical — Same day'),
    ], default='medium', required=True, tracking=True)
    budget_remaining = fields.Monetary(
        related='cost_center_id.balance',
        string='Remaining Budget',
        readonly=True,
        currency_field='currency_id',
    )
    over_budget = fields.Boolean(
        compute='_compute_over_budget',
        store=True,
    )

    @api.depends('amount', 'budget_remaining')
    def _compute_over_budget(self):
        for request in self:
            request.over_budget = (
                request.amount > 0
                and request.budget_remaining > 0
                and request.amount > request.budget_remaining
            )

    @api.constrains('amount', 'budget_remaining')
    def _check_budget_threshold(self):
        for request in self:
            if request.over_budget and request.urgency != 'critical':
                raise ValidationError(
                    'This request exceeds the remaining budget '
                    'for cost center "%s". Only critical-urgency '
                    'requests can exceed budget limits.'
                    % request.cost_center_id.name
                )

Reporting and Analytics

The Approvals module includes a built-in reporting view accessible at Approvals → Reporting. It provides pivot and graph views of approval requests grouped by category, status, approver, and date. For custom reporting needs, you can extend the analysis model:

• Average approval time — measure the time between request_date and the last approver's approval_date
• Bottleneck identification — group by approver to find who has the most pending requests
• Category breakdown — see which approval types generate the most volume
• Over-budget requests — filter on the custom over_budget field to track policy exceptions

Portal Access for External Approvers

When use_portal is enabled in settings, external users (board members, external auditors, contractors) can view and approve requests through the Odoo portal without needing a full internal user license. They log in at /my/approvals and see only the requests assigned to them. Portal approvals carry the same audit weight as internal approvals — the approval.approver record tracks the portal user ID and timestamp identically.

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