Add VAT rate resolution and VAT amount difference for E-Document purchases

[ventselartur]

Why

When importing e-documents for purchase processing, the system did not automatically resolve VAT Product Posting Groups from extracted VAT rates. Users had to manually identify and assign the correct VAT posting group for each line, which was error-prone and time-consuming. Additionally, rounding differences between the document's total VAT and the computed line-level VAT amounts were not reconciled, leading to posting discrepancies.

Summary

• Added VAT Product Posting Group resolution during Prepare Draft — matches the extracted VAT rate against VAT Posting Setup entries (Normal VAT and Reverse Charge VAT only) for the vendor's VAT Bus. Posting Group
• Added [BC] VAT Prod. Posting Group and [BC] VAT Rate Mismatch fields on E-Document Purchase Line with OnValidate/OnLookup support
• Added VAT amount difference computation and application to purchase lines when finalizing drafts, respecting Allow VAT Difference and Max. VAT Difference Allowed settings
• Added "Resolve VAT Group Purch EDoc" and "Apply VAT Diff. For Purch EDoc" toggles on Purchases & Payables Setup
• Improved ADI handler to prefer the unambiguous taxRate field and properly disambiguate the tax field between percentage and monetary values
• Added comprehensive test codeunit E-Doc Purch. VAT Tests covering resolution, mismatch detection, OnValidate behavior, and VAT calculation type filtering
• Updated existing structured validation tests to reflect corrected VAT rate expectations

Fixes AB#619564

[github-actions]

$\textbf{🟠\ High\ Severity\ —\ Performance} \quad \color{gray}{\texttt{\small Iteration\ 1}}$

ApplyVATDifference called before invoice discount

ApplyVATDifferenceToLines is invoked before ApplyInvDiscBasedOnAmt (line 181), so every PurchaseLine."Inv. Discount Amount" is still 0 at distribution time. The subtraction PurchaseLine."Line Amount" - PurchaseLine."Inv. Discount Amount" in the helper is therefore dead code and the proportional basis always equals the gross line amount, ignoring document-level discounts.

Recommendation:

• Move ApplyVATDifferenceToLines to after PurchCalcDiscByType.ApplyInvDiscBasedOnAmt so invoice-discount amounts are already populated on the purchase lines when the VAT difference is distributed.

Suggested change

	EDocPurchaseDocumentHelper.ApplyVATDifferenceToLines(PurchaseHeader, EDocumentPurchaseHeader);
	PurchaseHeader.Modify();
	PurchCalcDiscByType.ApplyInvDiscBasedOnAmt(EDocumentPurchaseHeader."Total Discount", PurchaseHeader);
	EDocPurchaseDocumentHelper.ApplyVATDifferenceToLines(PurchaseHeader, EDocumentPurchaseHeader);
	exit(PurchaseHeader);

_{👍 useful · ❤️ especially valuable · 👎 wrong - reply with why}

[github-actions]

$\textbf{🟠\ High\ Severity\ —\ Performance} \quad \color{gray}{\texttt{\small Iteration\ 1}}$

VAT Difference set without Validate, skips BC checks

PurchaseLine."VAT Difference" := Round(...) is a direct field assignment that bypasses the OnValidate trigger and BC's internal purchase-line recalculation logic. This can leave VAT-related totals on the header inconsistent and will not respect any line-level VAT difference constraints.

Recommendation:

• Use PurchaseLine.Validate("VAT Difference", Round(VATDiffForLine, Currency."Amount Rounding Precision")) and then call PurchaseLine.Modify(true) to ensure all dependent fields are recalculated.

Suggested change

	PurchaseLine."VAT Difference" := Round(VATDiffForLine, Currency."Amount Rounding Precision");
	PurchaseLine.Validate("VAT Difference", Round(VATDiffForLine, Currency."Amount Rounding Precision"));
	VATDiffRemainder := VATDiffForLine - PurchaseLine."VAT Difference";
	PurchaseLine.Modify(true);

_{👍 useful · ❤️ especially valuable · 👎 wrong - reply with why}

[github-actions]

$\textbf{🟠\ High\ Severity\ —\ Performance} \quad \color{gray}{\texttt{\small Iteration\ 1}}$

ComputeTotalLineAmount uses default Round precision

Round(EDocPurchLine.Quantity * EDocPurchLine."Unit Price" - EDocPurchLine."Total Discount") uses BC's default 2-decimal rounding, while ApplyVATDifferenceToLines distributes using Currency."Amount Rounding Precision". For currencies with non-standard precision (e.g. JPY=0, BHD=3), the denominator will differ from the actual purchase line amounts, causing the sum of distributed VAT differences to diverge from Applied VAT Amount Diff..

Recommendation:

• Pass the currency's amount rounding precision into ComputeTotalLineAmount (or read it from the purchase header) and use it in the Round() call to stay consistent with ApplyVATDifferenceToLines.

Suggested change

	TotalLineAmount += Round(EDocPurchLine.Quantity * EDocPurchLine."Unit Price" - EDocPurchLine."Total Discount");
	TotalLineAmount += Round(
	EDocPurchLine.Quantity * EDocPurchLine."Unit Price" - EDocPurchLine."Total Discount",
	Currency."Amount Rounding Precision");

_{👍 useful · ❤️ especially valuable · 👎 wrong - reply with why}

[github-actions]

$\textbf{🟡\ Medium\ Severity\ —\ Performance} \quad \color{gray}{\texttt{\small Iteration\ 1}}$

TotalLineVATAmount uses default Round, ignores currency precision

LineVATAmount := Round(LineAmount * EDocumentPurchaseLine."VAT Rate" / 100) applies the default 2-decimal rounding, independent of the document's currency. For currencies with fewer decimals (JPY) or more (BHD), the computed TotalLineVATAmount will diverge from the actual purchase line VAT amounts, generating a spurious or inflated Applied VAT Amount Diff..

Recommendation:

• Retrieve the currency record for the e-document (or use the default amount rounding precision) and pass it as the second argument to Round().

Suggested change

	LineVATAmount := Round(LineAmount * EDocumentPurchaseLine."VAT Rate" / 100);
	LineVATAmount := Round(LineAmount * EDocumentPurchaseLine."VAT Rate" / 100, Currency."Amount Rounding Precision");

_{👍 useful · ❤️ especially valuable · 👎 wrong - reply with why}

[github-actions]

$\textbf{🟡\ Medium\ Severity\ —\ Performance} \quad \color{gray}{\texttt{\small Iteration\ 1}}$

Single-line VAT rate fallback uses header-level Sub Total

For a single-line document where VAT Rate = 0, the fallback computes VATRate = ("Total VAT" / "Sub Total") * 100 from header fields. If the header Sub Total includes charges or differs from the individual line's base (e.g. due to header discounts, rounding, or fees), the computed rate will be wrong and an incorrect VAT Prod. Posting Group will be assigned.

Recommendation:

• Prefer using the line's own Quantity * "Unit Price" - "Total Discount" as the denominator, falling back to the header Sub Total only when the line amount is zero.

Suggested change

	VATRate := Round((EDocumentPurchaseHeader."Total VAT" / EDocumentPurchaseHeader."Sub Total") * 100, 0.01);
	var LineBase: Decimal;
	LineBase := EDocumentPurchaseLine.Quantity * EDocumentPurchaseLine."Unit Price" - EDocumentPurchaseLine."Total Discount";
	if LineBase = 0 then
	LineBase := EDocumentPurchaseHeader."Sub Total";
	if LineBase > 0 then
	VATRate := Round((EDocumentPurchaseHeader."Total VAT" / LineBase) * 100, 0.01);

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[github-actions]

$\textbf{🟡\ Medium\ Severity\ —\ Performance} \quad \color{gray}{\texttt{\small Iteration\ 1}}$

RecordRef.GetTable() called on unpositioned record

In LogVATRateMismatch, VATPostingSetupRef.GetTable(VATPostingSetup) is called after filters are applied but without FindFirst(). The RecordRef captures the table metadata but holds no actual row, so .SetReferenceSource() produces an invalid or empty drilldown link in the activity log.

Recommendation:

• Either position the record with VATPostingSetup.FindFirst() before calling GetTable, or remove the reference source if no specific record is to be linked.

Suggested change

	VATPostingSetupRef.GetTable(VATPostingSetup);
	EDocPurchDocHelper.SetNormalReverseChargeFilter(VATPostingSetup, VendVATBusPostingGroupCode);
	if VATPostingSetup.FindFirst() then begin
	VATPostingSetupRef.GetTable(VATPostingSetup);
	ActivityLog.SetReferenceSource(Page::"VAT Posting Setup", VATPostingSetupRef);
	end;

_{👍 useful · ❤️ especially valuable · 👎 wrong - reply with why}

[github-actions]

$\textbf{🟡\ Medium\ Severity\ —\ Performance} \quad \color{gray}{\texttt{\small Iteration\ 1}}$

LogVATRateResolved: same unpositioned RecordRef issue

Identical to the LogVATRateMismatch problem: VATPostingSetupRef.GetTable(VATPostingSetup) is called after setting filters but before any FindFirst(), yielding a RecordRef with no current record and an invalid activity-log reference link.

Recommendation:

• Call VATPostingSetup.FindFirst() before VATPostingSetupRef.GetTable(VATPostingSetup) and guard with an if block, or pass the specific resolved record as a parameter.

Suggested change

	VATPostingSetupRef.GetTable(VATPostingSetup);
	EDocPurchDocHelper.SetNormalReverseChargeFilter(VATPostingSetup, VendVATBusPostingGroupCode);
	if VATPostingSetup.FindFirst() then begin
	VATPostingSetupRef.GetTable(VATPostingSetup);
	ActivityLog.SetReferenceSource(Page::"VAT Posting Setup", VATPostingSetupRef);
	end;

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[github-actions]

$\textbf{🟡\ Medium\ Severity\ —\ Performance} \quad \color{gray}{\texttt{\small Iteration\ 1}}$

ParsePercentageFromText prefix stripping is case-sensitive

CleanedText.StartsWith('VAT ') and StartsWith('Tax ') are case-sensitive in AL. Common real-world patterns like "vat 20%", "Vat 20%", or "tax 20%" will not match, causing Evaluate() to fail and returning -1, which silently falls through to the ambiguous tax monetary-amount field instead of the unambiguous taxRate field.

Recommendation:

• Convert the cleaned text to uppercase before the prefix checks, or use LowerCase() comparisons.

Suggested change

	if CleanedText.StartsWith('VAT ') then
	CleanedText := UpperCase(TaxRateText.Replace('%', '').Trim());
	if CleanedText.StartsWith('VAT ') then
	CleanedText := CopyStr(CleanedText, 5).Trim();
	if CleanedText.StartsWith('TAX ') then
	CleanedText := CopyStr(CleanedText, 5).Trim();
	if Evaluate(ParsedValue, CleanedText) then
	exit(ParsedValue);
	exit(-1);

_{👍 useful · ❤️ especially valuable · 👎 wrong - reply with why}

[github-actions]

$\textbf{🟡\ Medium\ Severity\ —\ Security} \quad \color{gray}{\texttt{\small Iteration\ 1}}$

Resolve VAT Group defaults false, Apply VAT Diff defaults true

After upgrade, existing tenants will have "Apply VAT Diff. For Purch EDoc" = true (explicit InitValue = true) but "Resolve VAT Group Purch EDoc" = false (no InitValue). VAT differences will be redistributed across lines that still carry the BC-default VAT Prod. Posting Group rather than the e-document-matched one, potentially resulting in incorrect VAT postings.

Recommendation:

• Either add InitValue = true to "Resolve VAT Group Purch EDoc" to match the paired field's default, or set InitValue = false on "Apply VAT Diff. For Purch EDoc" so both features are opt-in together.

Suggested change

	field(6104; "Resolve VAT Group Purch EDoc"; Boolean)
	field(6104; "Resolve VAT Group Purch EDoc"; Boolean)
	{
	Caption = 'Resolve VAT Product Group for Purch. E-Doc.';
	DataClassification = CustomerContent;
	InitValue = true;
	}

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[sorenfriisalexandersen]

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[Groenbech96]

I would consider not putting this on the table.
You can compute this easily, and arguably it will be more correct to not store a value, but always compute it (Stale values....)

VATAmountDiff := EDocumentPurchaseHeader."Total VAT" - TotalLineVATAmount;

My suggestion would be to have a set of functions that compute this diff, and then use those where needed.