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Using Numeral’s Tax Engine with Business Central

This article walks you through installing the Numeral connector for Microsoft Dynamics 365 Business Central and ensuring accurate sales tax is applied.

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Written by Sunil Iyer
Updated yesterday

Numeral's Business Central integration enables automatic sales tax calculation, transaction recording, and filing for documents created in your Business Central environment.

Prerequisites

  • A Microsoft Dynamics 365 Business Central environment (sandbox or production)

  • A Numeral account with an active subscription

Step 1: Start the Connection in Numeral

  1. Log in to your Numeral dashboard.

  2. Navigate to Connections and click Add Connection.

  3. Select Business Central from the list of available platforms.

  4. Click Connect to Business Central. Numeral will generate a unique API key for your connection.

Step 2: Download the Numeral Tax Extension

  1. In the connection modal, click Download Extension to download the Numeral Tax Extension .app file.

  2. In your Business Central environment, use the search bar to find Extension Management.

  3. Upload and install the downloaded .app file.

  4. Wait for the extension installation to complete.

Step 3: Assign Permissions

The extension includes a permission set called Numeral Tax - Admin. Assign it to any users who need to configure the extension or calculate tax:

  1. Search for Permission Sets in Business Central.

  2. Find Numeral Tax - Admin in the list.

  3. Assign it to the relevant users.

Step 4: Configure the Extension in Business Central

  1. In Business Central, search for and open the Numeral Tax Setup page.

  2. Enter the following settings:

    • API Endpoint: https://business-central-integration.numeralhq.com

    • API Key: Paste the API key from the Numeral connection modal (use the Copy Numeral API key button)

    • Enabled: Toggle to On

    • Test Mode: Toggle On to use test mode during initial setup. Tax calculations will use a test API key and won't affect production data. Turn this Off once you're ready for production.

    • Sync Products: When enabled, your full product catalog is automatically sent to Numeral in the background after a successful connection test. Enable this to ensure Numeral has up-to-date item information for accurate tax calculations

    • Backfill Historical Transactions: When enabled, past sales transactions are automatically sent to Numeral in the background after a successful connection test. Enable this to give Numeral a complete transaction history for reporting and compliance purposes.

    • Use the “Test Connection” to verify connectivity

Step 5: Finish the Connection in Numeral

  1. Return to the Numeral dashboard connection modal.

  2. Click Finish connection to activate the integration.

  3. A success confirmation appears, and Business Central will show in your connections list.

Using the Integration

Once connected, a Numeral Tax section appears on Sales Orders, Sales Invoices, and Sales Credit Memos. It displays:

  • Tax Status: Shows "Pending" (in amber) or "Calculated" (in green) to indicate whether Numeral tax has been calculated for the document.

  • Calculate Tax: A clickable link to trigger tax calculation.

Calculating Tax

  1. Open a Sales Order, Sales Invoice, or Sales Credit Memo.

  2. Ensure the document has a Ship-to Address with a valid address (street, city, state, postal code, country).

  3. Add at least one line item (Item or G/L Account type) with a quantity and unit price.

  4. In the Numeral Tax section, click "Click to calculate tax with Numeral".

  5. The Tax Status will update to "Calculated" and tax amounts will be distributed proportionally across your document lines.

Note: Recalculating tax on the same document updates the existing calculation — it does not create duplicates. You can recalculate as many times as needed before posting.

Posting a Document

When you post a Sales Order or Sales Invoice in Business Central:

  1. The extension verifies that tax has been calculated before allowing the post.

  2. During posting, Numeral tax amounts are applied to all lines and G/L entries automatically.

  3. After posting, the extension commits the tax transaction to Numeral for reporting and filing.

  4. The posted invoice will show a Numeral Tax section with the Numeral Document Id and Tax Amount (Numeral) for reference.

Voiding / Cancelling

If you cancel a posted invoice in Business Central, the extension automatically notifies Numeral to void the corresponding tax transaction.

Supported Document Types

  • Sales Orders

  • Sales Invoices

  • Sales Credit Memos

Tax Exemptions

If a customer is tax-exempt, ensure the taxExempt flag is set to true on the document and optionally provide the taxExemptionNumber. The integration will return zero tax for exempt transactions.

Demo Video 1: Adding Business Central Connection in Numeral Dashboard

https://www.loom.com/share/6b68c18cc41a4521903d544cd7eb3724

Demo Video 2 : Setting Up and Using Numeral Tax in Business Central: https://www.loom.com/share/d331bc23b9194c60a378c52385467fed

Troubleshooting

Issue

Resolution

"Numeral Tax Setup has not been configured"

Open the Numeral Tax Setup page and complete all fields.

"Numeral Tax Connector is not enabled"

Toggle Enabled to On in Numeral Tax Setup.

"Numeral API Key has not been configured"

Enter the API key from Numeral in the Numeral Tax Setup page.

"Numeral API Base URL has not been configured"

Enter the API Base URL in Numeral Tax Setup.

"API Base URL must start with https://"

Ensure the URL starts with https://. HTTP is not supported.

"Connection failed. Please verify your API Base URL and API Key"

Double-check the URL and API key. Ensure the connection is active in Numeral.

"Unsupported document type for Numeral tax calculation"

Only Sales Orders, Sales Invoices, and Sales Credit Memos are supported.

Tax Status stays "Pending"

Click the Calculate Tax link. Tax is not calculated automatically — it must be triggered manually.

Zero tax returned

Confirm the ship-to address includes a valid US state and zip code. Verify line items have non-zero quantities and amounts.

Extension not visible in BC

Verify the .app file was uploaded in Extension Management and the deployment completed. Check that you're running BC v27.5+.

Connection shows as incomplete in Numeral

Return to the Numeral dashboard and click Finish connection.

💬 Questions? Reach out to our team anytime via the messaging widget in your Numeral dashboard.

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