[WHT]-Withholding Tax is not deducted from Expense Report lines based on the Expense Category during posting - #9973

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Copilot resolve the merge conflicts in this pull request

$\textbf{🟡\ Medium\ Severity\ —\ Performance}$

The new OnAfterExpenseCategoryValidateEmployee subscriber calls ExpenseCategory.Get immediately on every validate of the Expense Category field, so clearing or re-entering the field still pays a database lookup unconditionally. Add a cheap blank-value guard before the Get and only hit the table when a category code is present.

Suggested fix (apply manually — could not be anchored as a one-click suggestion):

        if CheckWithholdingTaxDisabled() then
            exit;

        if Rec."Expense Category" = '' then begin
            Rec."Wthldg. Tax Prod. Post. Group" := '';
            exit;
        end;

        if ExpenseCategory.Get(Rec."Expense Category") then
            Rec."Wthldg. Tax Prod. Post. Group" := ExpenseCategory."Wthldg. Tax Prod. Post. Group"
        else
            Rec."Wthldg. Tax Prod. Post. Group" := '';

Knowledge:

• microsoft/knowledge/performance/guard-event-subscribers-before-db-call.md

Line mapping was unavailable, so this was posted as an issue comment.

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$\textbf{🟡\ Medium\ Severity\ —\ Agent}$

This PR introduces a second, parallel implementation of single/group withholding-tax GL posting logic. WHTExpReportPostHandler.PostWHTSingle/PostWHTGroup (new, ExpenseWithholdingTax app) closely mirrors the pre-existing WthldgTaxEmplSubscribers.PostEmployeeWithholdingTax/PostEmployeeWHTGroupEntries (WithholdingTax app): both resolve WHT group components, iterate Withholding Tax Group Line, compute compounded bases, and call GenJnlPostLine.InitGLEntry/InsertGLEntry with a negated tax amount against the payable WHT account. The two implementations already differ subtly (e.g. how the base/compounding accumulates and how the group-vs-single decision integrates with IsEmployeeWHTApplicable), which is a maintenance/architecture risk: a future fix to the withholding-tax calculation or posting rules would need to be applied in two places, and the two code paths can silently drift apart. This is a cross-cutting architecture concern spanning the (pre-existing) WithholdingTax posting domain and the new ExpenseWithholdingTax feature, not owned by any single leaf review domain; recommend extracting the shared single/group posting logic into one reusable procedure that both callers invoke.

Posting this finding as an issue comment because inline comment placement failed.

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$\textbf{🟡\ Medium\ Severity\ —\ Breaking\ Changes}$

Behavioral change to the shipped, non-local procedure IsEmployeeWHTApplicable in WHTEmployeeCalculation.Codeunit.al (WithholdingTax app, currently at version 29.0.0.0 with prior released history). Previously the procedure returned false outright whenever GenJnlLine."Wthldg. Tax Prod. Post. Group" was empty. That hard exit is now removed; IsApplicable defaults to true and is only overridden by the new OnAfterIsEmployeeWHTApplicable event (to which, elsewhere in this same PR, the sole subscriber has a broken signature — see the Events finding above, meaning the override may not even fire). For any journal line with no product posting group and no other applicable subscriber, the procedure's return value flips from false to true, so withholding tax may now be calculated where it previously was not. The procedure's external signature is unchanged, so this is a behavior contract change rather than a compile-time break, but it can silently alter WHT calculation outcomes for existing customers/extensions relying on the old behavior. Flagging as a candidate for a curated breaking-change rule on behavior-only contract changes to shipped procedures.

Line mapping was unavailable, so this was posted as an issue comment.

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