This task is one section of Odoo accounting: nine everyday tasks, step by step, with 8 related tasks on one page.
1. Start from a real tax
Use a tax that already exists on the product. Do not invent a percentage. The product tax guide shows where to set it.
2. Map it
Open Accounting → Configuration → Fiscal Positions and create the position. Then open Accounting → Configuration → Taxes and open the tax that customer should bear. Set its Fiscal Position to the position you created, and set Replaces to the tax already on the product. Do not type a new percentage.
3. Assign the customer
Open Accounting → Customers → Customers, select the test customer, and set Fiscal Position on the Sales & Purchase tab. Leave other customers empty. On one document, you can instead set Fiscal Position on the Other Info tab before you add product lines.
4. Read the draft
Invoice the product to that customer. The tax on the draft should be the mapped tax. A second customer without the position should still get the product tax.
5. Frequently asked questions
Will this change every customer?
No. Only customers with the position, or documents where you set it.
What if I am unsure of the rate?
Ask the accountant before you map it. A wrong map posts the wrong tax on every invoice for that customer.
Does the position apply to old invoices?
Check a new draft. Do not assume posted invoices were rewritten.
6. Related articles and next steps
Odoo documents positions in the Odoo 19 fiscal positions page and the replacement itself on the taxes page.
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