[Event Request] - Add OnBeforeCalcRevChargeVATAmountInPurchLine (IsHandled) in Non-Deductible VAT

[skully1991]

Why do you need this change?

Within the Data Dynamic AG construct, there is a requirement to calculate the VAT amount based on custom business logic. For this reason, the event described below is needed.

Describe the request

• Add IntegrationEvent in codeunit 6200 "Non-Deductible VAT"
• Change procedure CalcRevChargeVATAmountInPurchLine in codeunit 6201 "Non-Ded. VAT Impl.".

New IntegrationEvent in codeunit 6200 "Non-Deductible VAT":

    [IntegrationEvent(false, false)]
    local procedure OnBeforeCalcRevChargeVATAmountInPurchLine(PurchaseLine: Record "Purchase Line"; var IsHandled: Boolean; var VATAmount: Decimal)
    begin
    end;

Invoke the new event in the local procedure CalcRevChargeVATAmountInPurchLine in codeunit 6201 "Non-Ded. VAT Impl.".

    local procedure CalcRevChargeVATAmountInPurchLine(PurchaseLine: Record "Purchase Line") VATAmount: Decimal;
    var
        VATPostingSetup: Record "VAT Posting Setup";
        Currency: Record Currency;
        IsHandled: Boolean;
    begin
        //Add new IntegrationEvent begin
        NonDeductibleVAT.OnBeforeCalcRevChargeVATAmountInPurchLine(PurchaseLine, IsHandled, VATAmount);
        If IsHandled then
            exit(VATAmount);
        //Add new IntegrationEvent end

        VATPostingSetup.Get(PurchaseLine."VAT Bus. Posting Group", PurchaseLine."VAT Prod. Posting Group");
        Currency.Initialize(PurchaseLine."Currency Code", true);
        VATAmount :=
            Round(
                PurchaseLine.Amount * VATPostingSetup."VAT %" / 100,
                Currency."Amount Rounding Precision", Currency.VATRoundingDirection());
    end;

Internal work item: AB#632747

[tomasevicst]

Hi Skully (@skully1991),

Thanks for submitting this extensibility request. To help us process it efficiently, please update the issue to include the required information.

📚 Extensibility Guidelines

Missing Information:

• Alternatives Evaluated: Please describe which existing events or extensibility patterns you evaluated and why they are insufficient for this scenario.
• Justification for IsHandled: Please explain why a regular event is not sufficient, which exact standard logic must be bypassed or replaced, and why that bypass is necessary.
• Performance Considerations: Please state how often this code path is expected to run and whether you expect any performance impact.
• Data Sensitivity Review: Please confirm whether any sensitive data would be exposed through the requested event.
• Multi-Extension Interaction: Please describe whether you expect conflicts if multiple extensions subscribe and how that risk would be handled.

Please update the issue with the missing details. We'll automatically re-analyze once updated.

[skully1991]

Hi tomasevicst,

thanks for the follow-up – here is the missing information in more detail:

1. What is the scenario you are trying to solve?
We are working with multiple country-specific VAT customizations.
In our implementation, the applicable VAT is not only derived from the standard setup, but also from a custom VAT history table.

Additionally, we support a “flat-rate VAT” model, where the VAT calculation deviates from the standard percentage-based logic.

Because of this, we need to be able to control how the VAT amount is calculated in purchase documents, especially in reverse charge scenarios.

---

2. What is the current problem?
The VAT amount is currently calculated using fixed standard logic:

VATAmount :=
    Round(
        PurchaseLine.Amount * VATPostingSetup."VAT %" / 100,
        Currency."Amount Rounding Precision", Currency.VATRoundingDirection());

This does not allow us to:

• apply VAT rates from our VAT history table
• support flat-rate VAT calculations
• override the calculation logic in a clean and controlled way

As a result, the calculated VAT amount is incorrect for our business scenarios.

---

3. Why are existing events not sufficient?
We analyzed the flow around CalcRevChargeVATAmountInPurchLine, but:

• there are no integration events at the point where the VAT amount is actually calculated

• available events (if any) are either:

  • too early (before all relevant data is available), or
  • too late (after VAT amount is already calculated and applied)

Therefore, we currently have no way to:

• replace the VAT calculation logic
• inject custom logic based on our VAT history or flat-rate rules

---

4. What is the requested extensibility (event)?
We request an IntegrationEvent directly at the point of VAT amount calculation in the reverse charge logic.

Example (simplified):

[IntegrationEvent(false, false)]
local procedure OnBeforeCalcRevChargeVATAmountInPurchLine(PurchaseLine: Record "Purchase Line"; var VATAmount: Decimal; var IsHandled: Boolean)

This would allow us to:

• fully override the VAT calculation
• apply VAT from custom history tables
• support flat-rate VAT scenarios
• avoid duplicating standard logic

---

5. Why is this important?
VAT calculation is a core accounting function and often subject to country-specific requirements.

In our case:

• VAT must be derived dynamically (history-based)
• flat-rate VAT models must be supported
• standard percentage-based calculation is not sufficient

Without an extensibility point, the only option is duplicating large parts of the logic

This is not upgrade-safe and increase maintenance effort significantly.

---

6. Additional considerations

• No performance impact is expected, as the event would only be triggered during standard calculation flow
• No sensitive data is exposed beyond what is already available in the current context

---

[tomasevicst]

Hi Skully (@skully1991),

Thanks for submitting this extensibility request. To help us process it efficiently, please update the issue to include the required information.

📚 Extensibility Guidelines

Missing Information:

• Multi-Extension Interaction: Please describe whether you expect conflicts if multiple extensions subscribe to this new IsHandled event and how that risk would be handled.

Please update the issue with the missing details. We'll automatically re-analyze once updated.

[skully1991]

Hi tomasevicst,

thank you for the review.

Regarding multi-extension interaction:

The event follows the standard IsHandled pattern. If multiple subscribers exist, AL event execution order is not guaranteed. In case one subscriber sets IsHandled = true, the base implementation will be skipped. Any further subscribers will still be invoked, but should respect the IsHandled state accordingly.

The intended usage of this event is to allow a single extension to fully override the VAT amount calculation logic in this scenario. We do not expect concurrent independent modifications of the same calculation logic.

---

As an alternative design, instead of a pre-processing IsHandled event, a post-processing event with 'PurchaseLine' and 'VATAmount' parameters could be introduced after the calculation logic:

local procedure CalcRevChargeVATAmountInPurchLine(PurchaseLine: Record "Purchase Line") VATAmount: Decimal;
var
    VATPostingSetup: Record "VAT Posting Setup";
    Currency: Record Currency;
begin
    VATPostingSetup.Get(PurchaseLine."VAT Bus. Posting Group", PurchaseLine."VAT Prod. Posting Group");
    Currency.Initialize(PurchaseLine."Currency Code", true);

    VATAmount :=
        Round(
            PurchaseLine.Amount * VATPostingSetup."VAT %" / 100,
            Currency."Amount Rounding Precision",
            Currency.VATRoundingDirection());

    //Add new post-processing event
    NonDeductibleVAT.OnAfterCalcRevChargeVATAmountInPurchLine(PurchaseLine, VATAmount);
end;

This would allow extensions to adjust the calculated VAT amount after the standard logic has been applied, without requiring suppression of the base implementation.

Best regards

[tomasevicst]

✅ Analysis complete - approved for implementation

---

Implementation:

Add a new integration event in the CalcRevChargeVATAmountInPurchLine() procedure of Codeunit 6201 Non-Ded. VAT Impl. after the standard reverse-charge VAT amount is calculated.

Location in CalcRevChargeVATAmountInPurchLine() procedure (around line 887):

local procedure CalcRevChargeVATAmountInPurchLine(PurchaseLine: Record "Purchase Line") VATAmount: Decimal;
var
    VATPostingSetup: Record "VAT Posting Setup";
    Currency: Record Currency;
begin
    VATPostingSetup.Get(PurchaseLine."VAT Bus. Posting Group", PurchaseLine."VAT Prod. Posting Group");
    Currency.Initialize(PurchaseLine."Currency Code", true);
    VATAmount :=
        Round(
            PurchaseLine.Amount * VATPostingSetup."VAT %" / 100,
            Currency."Amount Rounding Precision", Currency.VATRoundingDirection());
    NonDeductibleVAT.OnAfterCalcRevChargeVATAmountInPurchLine(PurchaseLine, VATAmount);
end;

Event Publisher (add at the end of the codeunit with other events):

[IntegrationEvent(false, false)]
internal procedure OnAfterCalcRevChargeVATAmountInPurchLine(PurchaseLine: Record "Purchase Line"; var VATAmount: Decimal)
begin
end;

---

File: NonDedVATImpl.Codeunit.al, NonDeductibleVAT.Codeunit.al

[AleksandricMarko]

Thanks for reporting this. We agree, and we’ll publish a fix asap, either in an update for the current version or in the next major release. Please do not reply to this, as we do not monitor closed issues. If you have follow-up questions or requests, please create a new issue where you reference this one.