diff --git a/components/cart/CartItem/CartItem.tsx b/components/cart/CartItem/CartItem.tsx
index 71ab58966..1e9062e91 100644
--- a/components/cart/CartItem/CartItem.tsx
+++ b/components/cart/CartItem/CartItem.tsx
@@ -5,6 +5,7 @@ import Link from 'next/link'
 import s from './CartItem.module.css'
 import { Trash, Plus, Minus } from '@components/icons'
 import { useUI } from '@components/ui/context'
+import type { LineItem } from '@framework/types'
 import usePrice from '@framework/product/use-price'
 import useUpdateItem from '@framework/cart/use-update-item'
 import useRemoveItem from '@framework/cart/use-remove-item'
diff --git a/framework/bigcommerce/api/cart/handlers/update-item.ts b/framework/bigcommerce/api/cart/handlers/update-item.ts
index df9ccaee8..b0ccc710b 100644
--- a/framework/bigcommerce/api/cart/handlers/update-item.ts
+++ b/framework/bigcommerce/api/cart/handlers/update-item.ts
@@ -14,6 +14,9 @@ const updateItem: CartHandlers['updateItem'] = async ({
     })
   }
 
+  console.log('ITEM', item)
+  console.log('AFTER', parseCartItem(item))
+
   const { data } = await config.storeApiFetch(
     `/v3/carts/${cartId}/items/${itemId}`,
     {
diff --git a/framework/bigcommerce/api/cart/index.ts b/framework/bigcommerce/api/cart/index.ts
index 8988f3606..0f0365cc3 100644
--- a/framework/bigcommerce/api/cart/index.ts
+++ b/framework/bigcommerce/api/cart/index.ts
@@ -8,6 +8,7 @@ import getCart from './handlers/get-cart'
 import addItem from './handlers/add-item'
 import updateItem from './handlers/update-item'
 import removeItem from './handlers/remove-item'
+import type { Cart, UpdateCartItemHandlerBody } from '../../types'
 
 type OptionSelections = {
   option_id: Number
@@ -23,40 +24,12 @@ export type ItemBody = {
 
 export type AddItemBody = { item: ItemBody }
 
-export type UpdateItemBody = { itemId: string; item: ItemBody }
-
 export type RemoveItemBody = { itemId: string }
 
-// TODO: this type should match:
-// https://developer.bigcommerce.com/api-reference/cart-checkout/server-server-cart-api/cart/getacart#responses
-export type Cart = {
-  id: string
-  parent_id?: string
-  customer_id: number
-  email: string
-  currency: { code: string }
-  tax_included: boolean
-  base_amount: number
-  discount_amount: number
-  cart_amount: number
-  line_items: {
-    custom_items: any[]
-    digital_items: any[]
-    gift_certificates: any[]
-    physical_items: any[]
-  }
-  created_time: string
-  discounts?: { id: number; discounted_amount: number }[]
-  // TODO: add missing fields
-}
-
 export type CartHandlers = {
   getCart: BigcommerceHandler<Cart, { cartId?: string }>
   addItem: BigcommerceHandler<Cart, { cartId?: string } & Partial<AddItemBody>>
-  updateItem: BigcommerceHandler<
-    Cart,
-    { cartId?: string } & Partial<UpdateItemBody>
-  >
+  updateItem: BigcommerceHandler<Cart, UpdateCartItemHandlerBody>
   removeItem: BigcommerceHandler<
     Cart,
     { cartId?: string } & Partial<RemoveItemBody>
diff --git a/framework/bigcommerce/api/utils/parse-item.ts b/framework/bigcommerce/api/utils/parse-item.ts
index 8a50881b1..dcc716c23 100644
--- a/framework/bigcommerce/api/utils/parse-item.ts
+++ b/framework/bigcommerce/api/utils/parse-item.ts
@@ -1,14 +1,21 @@
 import type { ItemBody as WishlistItemBody } from '../wishlist'
-import type { ItemBody } from '../cart'
+import type { CartItemBody, OptionSelections } from '../../types'
+
+type BCCartItemBody = {
+  product_id: number
+  variant_id: number
+  quantity?: number
+  option_selections?: OptionSelections
+}
 
 export const parseWishlistItem = (item: WishlistItemBody) => ({
   product_id: item.productId,
   variant_id: item.variantId,
 })
 
-export const parseCartItem = (item: ItemBody) => ({
+export const parseCartItem = (item: CartItemBody): BCCartItemBody => ({
   quantity: item.quantity,
-  product_id: item.productId,
-  variant_id: item.variantId,
+  product_id: Number(item.productId),
+  variant_id: Number(item.variantId),
   option_selections: item.optionSelections,
 })
diff --git a/framework/bigcommerce/cart/use-update-item.tsx b/framework/bigcommerce/cart/use-update-item.tsx
index 88a5b8c9d..6592b090f 100644
--- a/framework/bigcommerce/cart/use-update-item.tsx
+++ b/framework/bigcommerce/cart/use-update-item.tsx
@@ -1,14 +1,16 @@
 import { useCallback } from 'react'
 import debounce from 'lodash.debounce'
 import type { HookFetcher } from '@commerce/utils/types'
-import { CommerceError } from '@commerce/utils/errors'
+import { ValidationError } from '@commerce/utils/errors'
 import useCartUpdateItem from '@commerce/cart/use-update-item'
 import { normalizeCart } from '../lib/normalize'
 import type {
-  ItemBody,
-  UpdateItemBody,
-  Cart as BigcommerceCart,
-} from '../api/cart'
+  UpdateCartItemBody,
+  UpdateCartItemInput,
+  Cart,
+  BigcommerceCart,
+  LineItem,
+} from '../types'
 import { fetcher as removeFetcher } from './use-remove-item'
 import useCart from './use-cart'
 
@@ -17,9 +19,7 @@ const defaultOpts = {
   method: 'PUT',
 }
 
-export type UpdateItemInput = Partial<{ id: string } & ItemBody>
-
-export const fetcher: HookFetcher<Cart | null, UpdateItemBody> = async (
+export const fetcher: HookFetcher<Cart | null, UpdateCartItemBody> = async (
   options,
   { itemId, item },
   fetch
@@ -30,12 +30,12 @@ export const fetcher: HookFetcher<Cart | null, UpdateItemBody> = async (
       return removeFetcher(null, { itemId }, fetch)
     }
   } else if (item.quantity) {
-    throw new CommerceError({
+    throw new ValidationError({
       message: 'The item quantity has to be a valid integer',
     })
   }
 
-  const data = await fetch<BigcommerceCart>({
+  const data = await fetch<BigcommerceCart, UpdateCartItemBody>({
     ...defaultOpts,
     ...options,
     body: { itemId, item },
@@ -45,26 +45,41 @@ export const fetcher: HookFetcher<Cart | null, UpdateItemBody> = async (
 }
 
 function extendHook(customFetcher: typeof fetcher, cfg?: { wait?: number }) {
-  const useUpdateItem = (item?: any) => {
+  const useUpdateItem = <T extends LineItem | undefined = undefined>(
+    item?: T
+  ) => {
     const { mutate } = useCart()
-    const fn = useCartUpdateItem<Cart | null, UpdateItemBody>(
+    const fn = useCartUpdateItem<Cart | null, UpdateCartItemBody>(
       defaultOpts,
       customFetcher
     )
 
     return useCallback(
-      debounce(async (input: UpdateItemInput) => {
-        const data = await fn({
-          itemId: input.id ?? item?.id,
-          item: {
-            productId: input.productId ?? item?.product_id,
-            variantId: input.productId ?? item?.variant_id,
-            quantity: input.quantity,
-          },
-        })
-        await mutate(data, false)
-        return data
-      }, cfg?.wait ?? 500),
+      debounce(
+        async (
+          input: T extends LineItem
+            ? Partial<UpdateCartItemInput>
+            : UpdateCartItemInput
+        ) => {
+          const itemId = input.id ?? item?.id
+          const productId = input.productId ?? item?.productId
+          const variantId = input.productId ?? item?.variantId
+
+          if (!itemId || !productId || !variantId) {
+            throw new ValidationError({
+              message: 'Invalid input used for this operation',
+            })
+          }
+
+          const data = await fn({
+            itemId,
+            item: { productId, variantId, quantity: input.quantity },
+          })
+          await mutate(data, false)
+          return data
+        },
+        cfg?.wait ?? 500
+      ),
       [fn, mutate]
     )
   }
diff --git a/framework/bigcommerce/lib/normalize.ts b/framework/bigcommerce/lib/normalize.ts
index ec0f73a86..89aed2c38 100644
--- a/framework/bigcommerce/lib/normalize.ts
+++ b/framework/bigcommerce/lib/normalize.ts
@@ -1,4 +1,4 @@
-import type { Cart as BigcommerceCart } from '../api/cart'
+import type { Cart, BigcommerceCart, LineItem } from '../types'
 import update from './immutability'
 
 function normalizeProductOption(productOption: any) {
@@ -90,6 +90,7 @@ function normalizeLineItem(item: any): LineItem {
   return {
     id: item.id,
     variantId: String(item.variant_id),
+    productId: String(item.product_id),
     name: item.name,
     quantity: item.quantity,
     variant: {
diff --git a/framework/bigcommerce/types.d.ts b/framework/bigcommerce/types.d.ts
deleted file mode 100644
index d987381e7..000000000
--- a/framework/bigcommerce/types.d.ts
+++ /dev/null
@@ -1,5 +0,0 @@
-interface Cart extends BaseCart {
-  lineItems: LineItem[]
-}
-
-interface LineItem extends BaseLineItem {}
diff --git a/framework/bigcommerce/types.ts b/framework/bigcommerce/types.ts
new file mode 100644
index 000000000..766f2dbe9
--- /dev/null
+++ b/framework/bigcommerce/types.ts
@@ -0,0 +1,54 @@
+import * as Core from '@commerce/types'
+
+// TODO: this type should match:
+// https://developer.bigcommerce.com/api-reference/cart-checkout/server-server-cart-api/cart/getacart#responses
+export type BigcommerceCart = {
+  id: string
+  parent_id?: string
+  customer_id: number
+  email: string
+  currency: { code: string }
+  tax_included: boolean
+  base_amount: number
+  discount_amount: number
+  cart_amount: number
+  line_items: {
+    custom_items: any[]
+    digital_items: any[]
+    gift_certificates: any[]
+    physical_items: any[]
+  }
+  created_time: string
+  discounts?: { id: number; discounted_amount: number }[]
+  // TODO: add missing fields
+}
+
+export interface Cart extends Core.Cart {
+  lineItems: LineItem[]
+}
+
+export interface LineItem extends Core.LineItem {}
+
+/**
+ * Cart mutations
+ */
+
+export type OptionSelections = {
+  option_id: number
+  option_value: number | string
+}
+
+export interface CartItemBody extends Core.CartItemBody {
+  productId: string // The product id is always required for BC
+  optionSelections?: OptionSelections
+}
+
+export interface UpdateCartItemBody extends Core.UpdateCartItemBody {
+  item: CartItemBody
+}
+
+export interface UpdateCartItemInput
+  extends Core.UpdateCartItemInput<CartItemBody> {}
+
+export interface UpdateCartItemHandlerBody
+  extends Core.UpdateCartItemHandlerBody {}
diff --git a/framework/commerce/cart/use-cart.tsx b/framework/commerce/cart/use-cart.tsx
index ecc537539..94ccb73fc 100644
--- a/framework/commerce/cart/use-cart.tsx
+++ b/framework/commerce/cart/use-cart.tsx
@@ -1,15 +1,16 @@
 import Cookies from 'js-cookie'
 import type { HookInput, HookFetcher, HookFetcherOptions } from '../utils/types'
 import useData, { ResponseState, SwrOptions } from '../utils/use-data'
+import type { Cart } from '../types'
 import { useCommerce } from '..'
 
 export type CartResponse<Data> = ResponseState<Data> & { isEmpty?: boolean }
 
 export type CartInput = {
-  cartId?: BaseCart['id']
+  cartId?: Cart['id']
 }
 
-export default function useCart<Data extends BaseCart | null>(
+export default function useCart<Data extends Cart | null>(
   options: HookFetcherOptions,
   input: HookInput,
   fetcherFn: HookFetcher<Data, CartInput>,
diff --git a/framework/commerce/types.d.ts b/framework/commerce/types.d.ts
index 9bb996470..9e69ec25d 100644
--- a/framework/commerce/types.d.ts
+++ b/framework/commerce/types.d.ts
@@ -45,105 +45,6 @@ interface ProductPrice {
   extendedListPrice?: number
 }
 
-interface DiscountBase {
-  // The value of the discount, can be an amount or percentage
-  value: number
-}
-
-interface BaseLineItem {
-  id: string
-  variantId: string
-  name: string
-  quantity: number
-  discounts: DiscountBase[]
-  // A human-friendly unique string automatically generated from the product’s name
-  path: string
-  variant: BaseProductVariant
-}
-
-interface Measurement {
-  value: number
-  unit: 'KILOGRAMS' | 'GRAMS' | 'POUNDS' | 'OUNCES'
-}
-
-interface Image {
-  url: string
-  altText?: string
-  width?: number
-  height?: number
-}
-
-interface BaseProductVariant {
-  id: string
-  // The SKU (stock keeping unit) associated with the product variant.
-  sku: string
-  // The product variant’s title, or the product's name.
-  name: string
-  // Whether a customer needs to provide a shipping address when placing
-  // an order for the product variant.
-  requiresShipping: boolean
-  // The product variant’s price after all discounts are applied.
-  price: number
-  // Product variant’s price, as quoted by the manufacturer/distributor.
-  listPrice: number
-  // Image associated with the product variant. Falls back to the product image
-  // if no image is available.
-  image?: Image
-  // Indicates whether this product variant is in stock.
-  isInStock?: boolean
-  // Indicates if the product variant is available for sale.
-  availableForSale?: boolean
-  // The variant's weight. If a weight was not explicitly specified on the
-  // variant this will be the product's weight.
-  weight?: Measurement
-  // The variant's height. If a height was not explicitly specified on the
-  // variant, this will be the product's height.
-  height?: Measurement
-  // The variant's width. If a width was not explicitly specified on the
-  // variant, this will be the product's width.
-  width?: Measurement
-  // The variant's depth. If a depth was not explicitly specified on the
-  // variant, this will be the product's depth.
-  depth?: Measurement
-}
-
-// Shopping cart, a.k.a Checkout
-interface BaseCart {
-  id: string
-  // ID of the customer to which the cart belongs.
-  customerId?: string
-  // The email assigned to this cart
-  email?: string
-  // The date and time when the cart was created.
-  createdAt: string
-  // The currency used for this cart
-  currency: { code: string }
-  // Specifies if taxes are included in the line items.
-  taxesIncluded: boolean
-  lineItems: BaseLineItem[]
-  // The sum of all the prices of all the items in the cart.
-  // Duties, taxes, shipping and discounts excluded.
-  lineItemsSubtotalPrice: number
-  // Price of the cart before duties, shipping and taxes.
-  subtotalPrice: number
-  // The sum of all the prices of all the items in the cart.
-  // Duties, taxes and discounts included.
-  totalPrice: number
-  // Discounts that have been applied on the cart.
-  discounts?: DiscountBase[]
-}
-
-// TODO: Remove this type in favor of BaseCart
-interface Cart2 extends Entity {
-  id: string | undefined
-  currency: { code: string }
-  taxIncluded?: boolean
-  items: Pick<Product, 'id' | 'name' | 'prices'> & CartItem[]
-  subTotal: number | string
-  total: number | string
-  customerId: Customer['id']
-}
-
 interface CartItem extends Entity {
   quantity: number
   productId: Product['id']
diff --git a/framework/commerce/types.ts b/framework/commerce/types.ts
new file mode 100644
index 000000000..c662077a1
--- /dev/null
+++ b/framework/commerce/types.ts
@@ -0,0 +1,111 @@
+export interface Discount {
+  // The value of the discount, can be an amount or percentage
+  value: number
+}
+
+export interface LineItem {
+  id: string
+  variantId: string
+  productId: string
+  name: string
+  quantity: number
+  discounts: Discount[]
+  // A human-friendly unique string automatically generated from the product’s name
+  path: string
+  variant: ProductVariant
+}
+
+export interface Measurement {
+  value: number
+  unit: 'KILOGRAMS' | 'GRAMS' | 'POUNDS' | 'OUNCES'
+}
+
+export interface Image {
+  url: string
+  altText?: string
+  width?: number
+  height?: number
+}
+
+export interface ProductVariant {
+  id: string
+  // The SKU (stock keeping unit) associated with the product variant.
+  sku: string
+  // The product variant’s title, or the product's name.
+  name: string
+  // Whether a customer needs to provide a shipping address when placing
+  // an order for the product variant.
+  requiresShipping: boolean
+  // The product variant’s price after all discounts are applied.
+  price: number
+  // Product variant’s price, as quoted by the manufacturer/distributor.
+  listPrice: number
+  // Image associated with the product variant. Falls back to the product image
+  // if no image is available.
+  image?: Image
+  // Indicates whether this product variant is in stock.
+  isInStock?: boolean
+  // Indicates if the product variant is available for sale.
+  availableForSale?: boolean
+  // The variant's weight. If a weight was not explicitly specified on the
+  // variant this will be the product's weight.
+  weight?: Measurement
+  // The variant's height. If a height was not explicitly specified on the
+  // variant, this will be the product's height.
+  height?: Measurement
+  // The variant's width. If a width was not explicitly specified on the
+  // variant, this will be the product's width.
+  width?: Measurement
+  // The variant's depth. If a depth was not explicitly specified on the
+  // variant, this will be the product's depth.
+  depth?: Measurement
+}
+
+// Shopping cart, a.k.a Checkout
+export interface Cart {
+  id: string
+  // ID of the customer to which the cart belongs.
+  customerId?: string
+  // The email assigned to this cart
+  email?: string
+  // The date and time when the cart was created.
+  createdAt: string
+  // The currency used for this cart
+  currency: { code: string }
+  // Specifies if taxes are included in the line items.
+  taxesIncluded: boolean
+  lineItems: LineItem[]
+  // The sum of all the prices of all the items in the cart.
+  // Duties, taxes, shipping and discounts excluded.
+  lineItemsSubtotalPrice: number
+  // Price of the cart before duties, shipping and taxes.
+  subtotalPrice: number
+  // The sum of all the prices of all the items in the cart.
+  // Duties, taxes and discounts included.
+  totalPrice: number
+  // Discounts that have been applied on the cart.
+  discounts?: Discount[]
+}
+
+// Base cart item body used for cart mutations
+export interface CartItemBody {
+  variantId: string
+  productId?: string
+  quantity?: number
+}
+
+// Body by the update operation
+export interface UpdateCartItemBody {
+  itemId: string
+  item: CartItemBody
+}
+
+// Input expected by the `useUpdateItem` hook
+export type UpdateCartItemInput<T extends CartItemBody> = T & {
+  id: string
+}
+
+// Body expected by the update operation handler
+export interface UpdateCartItemHandlerBody extends Partial<UpdateCartItemBody> {
+  cartId?: string
+}
diff --git a/framework/commerce/utils/errors.ts b/framework/commerce/utils/errors.ts
index 76f899ab7..f4ab9fb9a 100644
--- a/framework/commerce/utils/errors.ts
+++ b/framework/commerce/utils/errors.ts
@@ -26,6 +26,14 @@ export class CommerceError extends Error {
   }
 }
 
+// Used for errors that come from a bad implementation of the hooks
+export class ValidationError extends CommerceError {
+  constructor(options: ErrorProps) {
+    super(options)
+    this.code = 'validation_error'
+  }
+}
+
 export class FetcherError extends CommerceError {
   status: number
 
diff --git a/framework/commerce/utils/types.ts b/framework/commerce/utils/types.ts
index 483b0c73c..010205f62 100644
--- a/framework/commerce/utils/types.ts
+++ b/framework/commerce/utils/types.ts
@@ -1,18 +1,18 @@
 // Core fetcher added by CommerceProvider
 export type Fetcher<T> = (options: FetcherOptions) => T | Promise<T>
 
-export type FetcherOptions = {
+export type FetcherOptions<Body = any> = {
   url?: string
   query?: string
   method?: string
   variables?: any
-  body?: any
+  body?: Body
 }
 
 export type HookFetcher<Data, Input = null, Result = any> = (
   options: HookFetcherOptions | null,
   input: Input,
-  fetch: <T = Result>(options: FetcherOptions) => Promise<T>
+  fetch: <T = Result, Body = any>(options: FetcherOptions<Body>) => Promise<T>
 ) => Data | Promise<Data>
 
 export type HookFetcherOptions = {