Hi
The issue why GST tax is not calculating on your purchase invoice likely stems from missing or incomplete configuration related to VAT Business Posting Group and proper linking of tax setup. In Microsoft Business Central, tax calculation depends on the combination of Tax Area Code, VAT Business Posting Group, and VAT Product Posting Group.
Verified Fix Steps for GST Tax Calculation
Assign VAT Business Posting Group to Vendor
Your screenshot shows the Vendor Tax Area Code is set and marked Tax Liable, but confirm the VAT Business Posting Group field on the Vendor card is selected and properly linked to tax setup.
Set VAT Business Posting Group on the Purchase Invoice Header
On the Purchase Invoice document, ensure that the VAT Bus. Posting Group (shown as empty in your screenshot) is set. This is critical for linking the vendor's posting group to tax calculation rules.
Verify Tax Setup Table Linking
Check that your VAT Business Posting Groups and VAT Product Posting Groups are linked properly in the VAT Business Posting Group – VAT Product Posting Group mapping with GST tax rates defined. Example:
- VAT Business Posting Group: Your vendor group (e.g., "VENDCAN")
- VAT Product Posting Group: The product or purchase group linked (e.g., "PURCHASE")
- Tax Area Code: GST
- Tax Percent: 5%
Confirm Tax Area Code and Tax Jurisdiction
Your Tax Area Code "GST" with Jurisdiction Code "GST" and Tax Group code is set for Sales and Use Tax at 5% is good. No changes needed here.
Lines Type and Tax Product Posting Group
- The line type is G/L Account, which is okay, but verify the VAT Product Posting Group for the G/L Account (Expense Account 61110) is set correctly to a group affecting tax calculation.
- Assign the VAT Product Posting Group on the G/L account card under the Posting tab.
Tax Calculation Enabled on Document
Ensure that the Tax Liable toggle is enabled on the document header, as you did. Also, check if any global tax calculation options or document-level toggles are overriding the tax calculation.
Thanks
Nimsara
