diff --git a/web-app/src/api/transaction.ts b/web-app/src/api/transaction.ts
index 07a8ad2..aac8dc8 100644
--- a/web-app/src/api/transaction.ts
+++ b/web-app/src/api/transaction.ts
@@ -165,6 +165,20 @@ export class TransactionApiClient extends ApiClient {
     return super.getJson(this.path + '/categories')
   }
 
+  async getCategoriesFlattened(): Promise<TransactionCategoryTree[]> {
+    const categories = await this.getCategories()
+    const flat: TransactionCategoryTree[] = []
+    await this.flattenCategories(flat, categories)
+    return flat
+  }
+
+  private flattenCategories(arr: TransactionCategoryTree[], tree: TransactionCategoryTree[]) {
+    for (const category of tree) {
+      arr.push(category)
+      this.flattenCategories(arr, category.children)
+    }
+  }
+
   getCategory(id: number): Promise<TransactionCategory> {
     return super.getJson(this.path + '/categories/' + id)
   }
diff --git a/web-app/src/components/CategorySelect.vue b/web-app/src/components/CategorySelect.vue
new file mode 100644
index 0000000..b665b71
--- /dev/null
+++ b/web-app/src/components/CategorySelect.vue
@@ -0,0 +1,31 @@
+<script setup lang="ts">
+import { TransactionApiClient, type TransactionCategoryTree } from '@/api/transaction';
+import { onMounted, ref, type Ref } from 'vue';
+
+
+const model = defineModel<number | null>({ required: true })
+defineProps<{ required?: boolean }>()
+defineEmits<{ categorySelected: [TransactionCategoryTree | null] }>()
+const categories: Ref<TransactionCategoryTree[]> = ref([])
+
+onMounted(() => {
+  const api = new TransactionApiClient()
+  api.getCategoriesFlattened()
+    .then(c => categories.value = c)
+})
+
+function getCategoryById(id: number): TransactionCategoryTree | null {
+  for (const c of categories.value) {
+    if (c.id === id) return c
+  }
+  return null
+}
+</script>
+<template>
+  <select v-model="model" @change="$emit('categorySelected', model === null ? null : getCategoryById(model))">
+    <option v-for="category in categories" :key="category.id" :value="category.id">
+      {{ "&nbsp;".repeat(4 * category.depth) + category.name }}
+    </option>
+    <option v-if="required !== true" :value="null" :selected="model === null">None</option>
+  </select>
+</template>
diff --git a/web-app/src/components/EditCategoryModal.vue b/web-app/src/components/EditCategoryModal.vue
index fc75d3d..292b219 100644
--- a/web-app/src/components/EditCategoryModal.vue
+++ b/web-app/src/components/EditCategoryModal.vue
@@ -6,6 +6,7 @@ import AppForm from './form/AppForm.vue';
 import FormGroup from './form/FormGroup.vue';
 import FormControl from './form/FormControl.vue';
 import AppButton from './AppButton.vue';
+import CategorySelect from './CategorySelect.vue';
 
 const props = defineProps<{
   category?: TransactionCategory
@@ -24,11 +25,16 @@ function show(): Promise<string | undefined> {
   name.value = props.category?.name ?? ''
   description.value = props.category?.description ?? ''
   if (props.category) {
+    name.value = props.category.name
+    description.value = props.category.description
     color.value = '#' + props.category.color
+    parentId.value = props.category.parentId
   } else {
+    name.value = ''
+    description.value = ''
     color.value = '#ffffff'
+    parentId.value = null
   }
-  parentId.value = props.category?.parentId ?? null
   return modal.value.show()
 }
 
@@ -85,6 +91,9 @@ defineExpose({ show })
           <FormControl label="Description" style="min-width: 300px;">
             <textarea v-model="description"></textarea>
           </FormControl>
+          <FormControl label="Parent Category">
+            <CategorySelect v-model="parentId"></CategorySelect>
+          </FormControl>
         </FormGroup>
       </AppForm>
     </template>
diff --git a/web-app/src/components/LineItemsEditor.vue b/web-app/src/components/LineItemsEditor.vue
index 5bd522b..5f49d76 100644
--- a/web-app/src/components/LineItemsEditor.vue
+++ b/web-app/src/components/LineItemsEditor.vue
@@ -11,20 +11,20 @@ import { formatMoney, type Currency } from '@/api/data';
 import ModalWrapper from './ModalWrapper.vue';
 import FormControl from './form/FormControl.vue';
 import { ref, type Ref, useTemplateRef } from 'vue';
+import CategorySelect from './CategorySelect.vue';
 
 const model = defineModel<TransactionDetailLineItem[]>({ required: true })
 defineProps<{
-  currency: Currency | null,
-  categories: TransactionCategoryTree[]
+  currency: Currency | null
 }>()
 
 const addLineItemDescription = ref('')
 const addLineItemValuePerItem = ref(0)
 const addLineItemQuantity = ref(0)
-const addLineItemCategory: Ref<TransactionCategoryTree | null> = ref(null)
+const addLineItemCategoryId: Ref<number | null> = ref(null)
+const selectedCategory: Ref<TransactionCategoryTree | null> = ref(null)
 const addLineItemModal = useTemplateRef('addLineItemModal')
 
-
 function canAddLineItem() {
   return addLineItemDescription.value.length > 0 &&
     addLineItemQuantity.value > 0
@@ -34,11 +34,11 @@ function showAddLineItemModal() {
   addLineItemDescription.value = ''
   addLineItemValuePerItem.value = 1.00
   addLineItemQuantity.value = 1
-  addLineItemCategory.value = null
+  addLineItemCategoryId.value = null
   addLineItemModal.value?.show()
 }
 
-function addLineItem() {
+async function addLineItem() {
   const idxs: number[] = model.value.map(i => i.idx)
   const newIdx = Math.max(...idxs)
   model.value.push({
@@ -46,7 +46,7 @@ function addLineItem() {
     description: addLineItemDescription.value,
     quantity: addLineItemQuantity.value,
     valuePerItem: addLineItemValuePerItem.value,
-    category: addLineItemCategory.value
+    category: selectedCategory.value
   })
   addLineItemModal.value?.close()
 }
@@ -104,12 +104,7 @@ function removeLineItem(idx: number) {
             <input type="number" step="1" min="1" v-model="addLineItemQuantity" />
           </FormControl>
           <FormControl label="Category">
-            <select v-model="addLineItemCategory">
-              <option v-for="category in categories" :key="category.id" :value="category">
-                {{ "&nbsp;".repeat(4 * category.depth) + category.name }}
-              </option>
-              <option :value="null">None</option>
-            </select>
+            <CategorySelect v-model="addLineItemCategoryId" @category-selected="c => selectedCategory = c" />
           </FormControl>
         </FormGroup>
       </template>
diff --git a/web-app/src/pages/CategoriesPage.vue b/web-app/src/pages/CategoriesPage.vue
index 4f16aa2..6e87df5 100644
--- a/web-app/src/pages/CategoriesPage.vue
+++ b/web-app/src/pages/CategoriesPage.vue
@@ -54,6 +54,7 @@ async function deleteCategory(categoryId: number) {
 
 async function addCategory() {
   editedCategory.value = undefined
+  await nextTick()
   const result = await editCategoryModal.value?.show()
   if (result === 'saved') {
     await loadCategories()
diff --git a/web-app/src/pages/forms/EditTransactionPage.vue b/web-app/src/pages/forms/EditTransactionPage.vue
index 6837be2..2c5d395 100644
--- a/web-app/src/pages/forms/EditTransactionPage.vue
+++ b/web-app/src/pages/forms/EditTransactionPage.vue
@@ -12,8 +12,9 @@ The form consists of a few main sections:
 <script setup lang="ts">
 import { AccountApiClient, type Account } from '@/api/account';
 import { DataApiClient, type Currency } from '@/api/data';
-import { TransactionApiClient, type AddTransactionPayload, type TransactionCategoryTree, type TransactionDetail, type TransactionDetailLineItem, type TransactionVendor } from '@/api/transaction';
+import { TransactionApiClient, type AddTransactionPayload, type TransactionDetail, type TransactionDetailLineItem, type TransactionVendor } from '@/api/transaction';
 import AppPage from '@/components/AppPage.vue';
+import CategorySelect from '@/components/CategorySelect.vue';
 import AppForm from '@/components/form/AppForm.vue';
 import FormActions from '@/components/form/FormActions.vue';
 import FormControl from '@/components/form/FormControl.vue';
@@ -38,7 +39,6 @@ const availableCurrencies = computed(() => {
   return allCurrencies.value.filter(c => allAccounts.value.some(a => a.currency === c.code))
 })
 const availableVendors: Ref<TransactionVendor[]> = ref([])
-const availableCategories: Ref<TransactionCategoryTree[]> = ref([])
 const allAccounts: Ref<Account[]> = ref([])
 const availableAccounts = computed(() => {
   return allAccounts.value.filter(a => a.currency === currency.value?.code)
@@ -77,19 +77,13 @@ watch(availableCurrencies, (newValue: Currency[]) => {
 onMounted(async () => {
   if (!profileStore.state) return
   const dataClient = new DataApiClient()
-  const transactionClient = new TransactionApiClient(profileStore.state)
+  const transactionClient = new TransactionApiClient()
   const accountClient = new AccountApiClient(profileStore.state)
 
   // Fetch various collections of data needed for different user choices.
   dataClient.getCurrencies().then(currencies => allCurrencies.value = currencies)
   transactionClient.getVendors().then(vendors => availableVendors.value = vendors)
   transactionClient.getAllTags().then(t => allTags.value = t)
-  transactionClient.getCategories().then(categories => {
-    // Flatten the recursive list of categories.
-    const flattened: TransactionCategoryTree[] = []
-    flattenCategories(flattened, categories)
-    availableCategories.value = flattened
-  })
   accountClient.getAccounts().then(accounts => allAccounts.value = accounts)
 
 
@@ -108,13 +102,6 @@ onMounted(async () => {
   }
 })
 
-function flattenCategories(arr: TransactionCategoryTree[], tree: TransactionCategoryTree[]) {
-  for (const category of tree) {
-    arr.push(category)
-    flattenCategories(arr, category.children)
-  }
-}
-
 /**
  * Submits the transaction. If the user is editing an existing transaction,
  * then that transaction will be updated. Otherwise, a new transaction is
@@ -140,7 +127,7 @@ async function doSubmit() {
     })
   }
 
-  const transactionApi = new TransactionApiClient(profileStore.state)
+  const transactionApi = new TransactionApiClient()
   let savedTransaction = null
   try {
     loading.value = true
@@ -291,12 +278,7 @@ function isEdited() {
           </select>
         </FormControl>
         <FormControl label="Category">
-          <select v-model="categoryId" :disabled="loading">
-            <option v-for="category in availableCategories" :key="category.id" :value="category.id">
-              {{ "&nbsp;".repeat(4 * category.depth) + category.name }}
-            </option>
-            <option :value="null" :selected="categoryId === null">None</option>
-          </select>
+          <CategorySelect v-model="categoryId" />
         </FormControl>
       </FormGroup>
 
@@ -320,7 +302,7 @@ function isEdited() {
         </FormControl>
       </FormGroup>
 
-      <LineItemsEditor v-model="lineItems" :currency="currency" :categories="availableCategories" />
+      <LineItemsEditor v-model="lineItems" :currency="currency" />
 
       <FormGroup>
         <!-- Tags -->