Apply tax rule when selecting category

src/components/MoneyRequestConfirmationList.tsx

@@ -672,10 +672,10 @@ function MoneyRequestConfirmationList({
         if (iouCategory || !shouldShowCategories || enabledCategories.length !== 1 || !isCategoryRequired) {
             return;
         }
-        IOU.setMoneyRequestCategory(transactionID, enabledCategories.at(0)?.name ?? '');
+        IOU.setMoneyRequestCategory(transactionID, enabledCategories.at(0)?.name ?? '', policy?.id);
         // Keep 'transaction' out to ensure that we autoselect the option only once
         // eslint-disable-next-line react-compiler/react-compiler, react-hooks/exhaustive-deps
-    }, [shouldShowCategories, policyCategories, isCategoryRequired]);
+    }, [shouldShowCategories, policyCategories, isCategoryRequired, policy?.id]);
 
     // Auto select the tag if there is only one enabled tag and it is required
     useEffect(() => {

src/libs/TransactionUtils/index.ts

@@ -9,7 +9,8 @@ import type {ValueOf} from 'type-fest';
 import {getPolicyCategoriesData} from '@libs/actions/Policy/Category';
 import {getPolicyTagsData} from '@libs/actions/Policy/Tag';
 import type {TransactionMergeParams} from '@libs/API/parameters';
-import {getCurrencyDecimals} from '@libs/CurrencyUtils';
+import {getCategoryDefaultTaxRate} from '@libs/CategoryUtils';
+import {convertToBackendAmount, getCurrencyDecimals} from '@libs/CurrencyUtils';
 import DateUtils from '@libs/DateUtils';
 import DistanceRequestUtils from '@libs/DistanceRequestUtils';
 import {toLocaleDigit} from '@libs/LocaleDigitUtils';
@@ -1239,6 +1240,23 @@ function buildTransactionsMergeParams(reviewDuplicates: OnyxEntry<ReviewDuplicat
     };
 }
 
+function getCategoryTaxCodeAndAmount(category: string, transaction: OnyxEntry<Transaction>, policy: OnyxEntry<Policy>) {
+    const taxRules = policy?.rules?.expenseRules?.filter((rule) => rule.tax);
+    if (!taxRules || taxRules?.length === 0) {
+        return {categoryTaxCode: undefined, categoryTaxAmount: undefined};
+    }
+
+    const categoryTaxCode = getCategoryDefaultTaxRate(taxRules, category, policy?.taxRates?.defaultExternalID);
+    const categoryTaxPercentage = getTaxValue(policy, transaction, categoryTaxCode ?? '');
+    let categoryTaxAmount;
+
+    if (categoryTaxPercentage) {
+        categoryTaxAmount = convertToBackendAmount(calculateTaxAmount(categoryTaxPercentage, getAmount(transaction), getCurrency(transaction)));
+    }
+
+    return {categoryTaxCode, categoryTaxAmount};
+}
+
 export {
     buildOptimisticTransaction,
     calculateTaxAmount,
@@ -1323,6 +1341,7 @@ export {
     hasReceiptSource,
     shouldShowAttendees,
     getFormattedPostedDate,
+    getCategoryTaxCodeAndAmount,
 };
 
 export type {TransactionChanges};

src/libs/actions/IOU.ts

@@ -564,8 +564,19 @@ function setMoneyRequestPendingFields(transactionID: string, pendingFields: Onyx
     Onyx.merge(`${ONYXKEYS.COLLECTION.TRANSACTION_DRAFT}${transactionID}`, {pendingFields});
 }
 
-function setMoneyRequestCategory(transactionID: string, category: string) {
+function setMoneyRequestCategory(transactionID: string, category: string, policyID?: string) {
     Onyx.merge(`${ONYXKEYS.COLLECTION.TRANSACTION_DRAFT}${transactionID}`, {category});
+    if (!policyID) {
+        setMoneyRequestTaxRate(transactionID, '');
+        setMoneyRequestTaxAmount(transactionID, null);
+        return;
+    }
+    const transaction = allTransactionDrafts[`${ONYXKEYS.COLLECTION.TRANSACTION_DRAFT}${transactionID}`];
+    const {categoryTaxCode, categoryTaxAmount} = TransactionUtils.getCategoryTaxCodeAndAmount(category, transaction, PolicyUtils.getPolicy(policyID));
+    if (categoryTaxCode && categoryTaxAmount !== undefined) {
+        setMoneyRequestTaxRate(transactionID, categoryTaxCode);
+        setMoneyRequestTaxAmount(transactionID, categoryTaxAmount);
+    }
 }
 
 function setMoneyRequestTag(transactionID: string, tag: string) {
@@ -3400,9 +3411,17 @@ function updateMoneyRequestCategory(
     policyTagList: OnyxEntry<OnyxTypes.PolicyTagLists>,
     policyCategories: OnyxEntry<OnyxTypes.PolicyCategories>,
 ) {
+    const transaction = allTransactions[`${ONYXKEYS.COLLECTION.TRANSACTION}${transactionID}`];
+    const {categoryTaxCode, categoryTaxAmount} = TransactionUtils.getCategoryTaxCodeAndAmount(category, transaction, policy);
     const transactionChanges: TransactionChanges = {
         category,
+        ...(categoryTaxCode &&
+            categoryTaxAmount !== undefined && {
+                taxCode: categoryTaxCode,
+                taxAmount: categoryTaxAmount,
+            }),
     };
+
     const {params, onyxData} = getUpdateMoneyRequestParams(transactionID, transactionThreadReportID, transactionChanges, policy, policyTagList, policyCategories);
     API.write(WRITE_COMMANDS.UPDATE_MONEY_REQUEST_CATEGORY, params, onyxData);
 }
@@ -5327,17 +5346,26 @@ function completeSplitBill(chatReportID: string, reportAction: OnyxTypes.ReportA
     Report.notifyNewAction(chatReportID, sessionAccountID);
 }
 
-function setDraftSplitTransaction(transactionID: string, transactionChanges: TransactionChanges = {}) {
+function setDraftSplitTransaction(transactionID: string, transactionChanges: TransactionChanges = {}, policy?: OnyxEntry<OnyxTypes.Policy>) {
+    const newTransactionChanges = {...transactionChanges};
     let draftSplitTransaction = allDraftSplitTransactions[`${ONYXKEYS.COLLECTION.SPLIT_TRANSACTION_DRAFT}${transactionID}`];
 
     if (!draftSplitTransaction) {
         draftSplitTransaction = allTransactions[`${ONYXKEYS.COLLECTION.TRANSACTION}${transactionID}`];
     }
 
+    if (transactionChanges.category) {
+        const {categoryTaxCode, categoryTaxAmount} = TransactionUtils.getCategoryTaxCodeAndAmount(transactionChanges.category, draftSplitTransaction, policy);
+        if (categoryTaxCode && categoryTaxAmount !== undefined) {
+            newTransactionChanges.taxCode = categoryTaxCode;
+            newTransactionChanges.taxAmount = categoryTaxAmount;
+        }
+    }
+
     const updatedTransaction = draftSplitTransaction
         ? TransactionUtils.getUpdatedTransaction({
               transaction: draftSplitTransaction,
-              transactionChanges,
+              transactionChanges: newTransactionChanges,
               isFromExpenseReport: false,
               shouldUpdateReceiptState: false,
           })

src/pages/iou/request/step/IOURequestStepCategory.tsx

@@ -68,7 +68,8 @@ function IOURequestStepCategory({
     const {translate} = useLocalize();
     const isEditing = action === CONST.IOU.ACTION.EDIT;
     const isEditingSplitBill = isEditing && iouType === CONST.IOU.TYPE.SPLIT;
-    const transactionCategory = ReportUtils.getTransactionDetails(isEditingSplitBill && !lodashIsEmpty(splitDraftTransaction) ? splitDraftTransaction : transaction)?.category;
+    const currentTransaction = isEditingSplitBill && !lodashIsEmpty(splitDraftTransaction) ? splitDraftTransaction : transaction;
+    const transactionCategory = ReportUtils.getTransactionDetails(currentTransaction)?.category;
 
     // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
     const reportAction = reportActions?.[report?.parentReportActionID || reportActionID] ?? null;
@@ -113,7 +114,7 @@ function IOURequestStepCategory({
         if (transaction) {
             // In the split flow, when editing we use SPLIT_TRANSACTION_DRAFT to save draft value
             if (isEditingSplitBill) {
-                IOU.setDraftSplitTransaction(transaction.transactionID, {category: updatedCategory});
+                IOU.setDraftSplitTransaction(transaction.transactionID, {category: updatedCategory}, policy);
                 navigateBack();
                 return;
             }
@@ -125,7 +126,7 @@ function IOURequestStepCategory({
             }
         }
 
-        IOU.setMoneyRequestCategory(transactionID, updatedCategory);
+        IOU.setMoneyRequestCategory(transactionID, updatedCategory, policy?.id);
 
         if (action === CONST.IOU.ACTION.CATEGORIZE) {
             Navigation.navigate(ROUTES.MONEY_REQUEST_STEP_CONFIRMATION.getRoute(action, iouType, transactionID, report?.reportID ?? '-1'));

src/pages/iou/request/step/IOURequestStepConfirmation.tsx

@@ -156,9 +156,9 @@ function IOURequestStepConfirmation({
             return;
         }
         if (policyCategories?.[transaction.category] && !policyCategories[transaction.category].enabled) {
-            IOU.setMoneyRequestCategory(transactionID, '');
+            IOU.setMoneyRequestCategory(transactionID, '', policy?.id);
         }
-    }, [policyCategories, transaction?.category, transactionID]);
+    }, [policy?.id, policyCategories, transaction?.category, transactionID]);
 
     const policyDistance = Object.values(policy?.customUnits ?? {}).find((customUnit) => customUnit.name === CONST.CUSTOM_UNITS.NAME_DISTANCE);
     const defaultCategory = policyDistance?.defaultCategory ?? '';
@@ -167,10 +167,10 @@ function IOURequestStepConfirmation({
         if (requestType !== CONST.IOU.REQUEST_TYPE.DISTANCE || !!transaction?.category) {
             return;
         }
-        IOU.setMoneyRequestCategory(transactionID, defaultCategory);
+        IOU.setMoneyRequestCategory(transactionID, defaultCategory, policy?.id);
         // Prevent resetting to default when unselect category
         // eslint-disable-next-line react-compiler/react-compiler, react-hooks/exhaustive-deps
-    }, [transactionID, requestType, defaultCategory]);
+    }, [transactionID, requestType, defaultCategory, policy?.id]);
 
     const navigateBack = useCallback(() => {
         // If the action is categorize and there's no policies other than personal one, we simply call goBack(), i.e: dismiss the whole flow together