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API v2.0 - Purchase Invoice Line - taxCode ignored

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Posted on by JM-19031351-0

) Context:

I am working with Business Central API v2 (Business Central 20.0 (Platform 20.0.37114.38150) to create and update purchaseInvoiceLines. However, I am experiencing issues with setting or modifying the taxCode field.

What I Have Tried:

Creating a Purchase Invoice Line with taxCode

I make a POST request to:

POST /purchaseInvoices({invoiceId})/purchaseInvoiceLines

with the following payload:

{
  "documentId": "37308e23-7fa6-ef11-a2e7-005056bed6cb",
  "accountId": "6539b815-4490-ef11-a2e6-005056bed6cb",
  "lineType": "Account",
  "lineObjectNumber": "73100",
  "description": "Igangværende arbejde",
  "unitCost": 200,
  "quantity": 1,
  "amountExcludingTax": 200,
  "taxCode": "FRITAGET"
}

Result: The invoice line is created, but the taxCode field remains empty.

Updating an Existing Line with taxCode
- After creating a line, I try updating the taxCode via:
```
PATCH /purchaseInvoices({invoiceId})/purchaseInvoiceLines({lineId})
```
  with:
```
{ "taxCode": "FRITAGET" }
```
- Result: No error is returned, but the taxCode is not updated.
Verifying taxCode and taxGroupId
- I confirmed via:
```
GET /companies({companyId})/taxGroups
```
  that "FRITAGET" is a valid tax group.
Additional Tests
- I verified that I can update other fields like quantity on the same line.
- Manually setting the tax code in the BC UI works fine

Questions:

Why does Business Central API ignore taxCode on purchaseInvoiceLines?
Is taxCode read-only after creation? If so, how should it be assigned?
Is there a workaround (e.g., using taxGroupId or another field) to ensure the correct tax code is applied?
Are there specific conditions (e.g., posting groups, tax setups) that could prevent taxCode from being set via API but allow it in the UI?
Is this behavior expected, or is it a limitation/bug in the BC API v2?

I would assume this was 100% basic functionality of any working ERP.

Thanks - any insights or official documentation references would be greatly appreciated.

Categories:

Dynamics 365 Business Central

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Suggested answer

Suresh Kulla 50,247 Super User 2025 Season 2 on at

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Please the below condition on that field, based on General Ledger Setup the value is copied to VAT Prod. Posting Group or Tax Group Code.

field(taxCode; Rec."Tax Code")
{
Caption = 'Tax Code';

trigger OnValidate()
var
GeneralLedgerSetup: Record "General Ledger Setup";
begin
if GeneralLedgerSetup.UseVat() then begin
Rec.Validate("VAT Prod. Posting Group", CopyStr(Rec."Tax Code", 1, 20));
RegisterFieldSet(Rec.FieldNo("VAT Prod. Posting Group"));
end else begin
Rec.Validate("Tax Group Code", CopyStr(Rec."Tax Code", 1, 20));
RegisterFieldSet(Rec.FieldNo("Tax Group Code"));
end;
end;
}

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Suggested answer

Khushbu Rajvi. 20,647 Super User 2025 Season 2 on at

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The taxCode field isn't directly stored but mapped to either VAT Prod. Posting Group or Tax Group Code, based on the Use VAT setting in General Ledger Setup. The API likely ignores taxCode because it's validated and reassigned internally. Try updating VAT Prod. Posting Group (if VAT is enabled) or Tax Group Code (if VAT is disabled) instead of taxCode in your API request.

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YUN ZHU 95,748 Super User 2025 Season 2 on at

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Hi, you can try the following function.

Configure API Templates - Business Central | Microsoft Learn

Thanks.

ZHU

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CU19021242-1 12 on at

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Hi,

I have a very similar problem with the "taxCode" field when creating a purchase invoice through API V2. What I'm finding is :

1. If I populate "taxCode" with a 'VAT Prod. Posting Group' code which doesn't exist, I rightly get an "Internal_TableRelation" error because the value doesn't exist.

2. If I populate "taxCode" with a 'VAT Prod. Posting Group' code which does exist, I get "The VAT Posting Setup does not exist. Identification fields and values: VAT Bus. Posting Group='DOMESTIC',VAT Prod. Posting Group='' ". So it thinks I have passed it a blank value for this field.

Did you get anywhere with figuring out what the problem is?

Thanks.

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