1. Verify User Access Rights

Ensure that your user account has the necessary permissions to view and edit fiscal positions:

• Navigate to: Settings → Users & Companies → Users.
• Select your user and check the following access rights:
  • Accounting: Should be set to Accountant or Advisor.
  • Technical Features: Ensure this is enabled if available.

Insufficient permissions can restrict access to certain configuration tabs, including Tax Mapping.

 2. Activate Developer Mode

Some configuration options are only visible in Developer Mode:

• Activate Developer Mode:
  • Go to Settings → General Settings.
  • Scroll down and click on Activate the developer mode.

Once activated, revisit the Fiscal Positions configuration to see if the Tax Mapping tab appears.

 3. Check for Active Taxes

The Tax Mapping feature relies on active tax records:

• Navigate to: Accounting → Configuration → Taxes.
• Ensure that the taxes you intend to map are active.

Inactive taxes won't appear in the mapping options, which might cause the Tax Mapping tab to be hidden or non-functional.

 4. Review Installed Modules

Certain modules or localization packages might affect the visibility of configuration tabs:

• Check Installed Modules:
  • Go to Apps.
  • Search for any installed localization modules that might override default behaviors.

If a specific localization module is causing the issue, consider consulting its documentation or support resources.

 5. Inspect for Customizations or Third-Party Modules

Custom modules or third-party add-ons might alter the standard behavior of Odoo:

• Review Custom Modules:
  • Navigate to Apps.
  • Filter by Custom Modules to identify any non-standard installations.

If a custom module is responsible, you may need to adjust its code or consult with the developer.

 6. Consult Odoo Documentation

Refer to the official Odoo documentation for detailed guidance on configuring Fiscal Positions and Tax Mapping:

• Odoo 18.0 Fiscal Positions Documentation

This resource provides comprehensive information on setting up and managing tax and account mappings.

Hii,

1. Activate Developer Mode (first step always)

Some advanced configuration tabs like "Tax Mapping" only show when Developer Mode is activated.

How to activate:

• Go to Settings
• Scroll to the bottom and click “Activate Developer Mode” (or use the ⚙️ menu if already active)

Now go back to Accounting → Configuration → Fiscal Positions, open a fiscal position — the Tax Mapping tab should appear.

. Enable Accounting Features

Ensure your system is using full accounting features.

Go to:

• Settings → Accounting
• Enable:
  • ✅ TaxCloud (optional for USA tax automation)
  • ✅ Taxes (obviously should be active)
  • ✅ Fiscal Positions

If using Invoicing instead of full Accounting module, switch to the full accounting app.

Fiscal Position Type Must Be "Tax Mapping"

Make sure the Fiscal Position is not just for account mapping.

When you create or edit a fiscal position:

• Set "Use Tax Mapping" = ✅ Checked
• Odoo conditionally hides the tax mapping tab if this option is off or if you’re in a limited feature mode.

Install “Invoicing” or “Accounting” App

In some cases (especially in Odoo 14+ CE), the tax mapping logic is hidden unless you install the full Invoicing or Accounting app.

To install:

• Go to Apps
• Search for Invoicing or Accounting
• Install it

Once installed, you will see tax configuration and mapping features.

You're Using the Website Sale / eCommerce Fiscal Mapping

If you're configuring fiscal positions from Website → Configuration → Fiscal Positions, these might not show full tax/account mapping tabs, as they're meant for simplified website behavior.

Instead, use:

• Accounting → Configuration → Fiscal Positions

i hope it is helpfull