diff --git a/src/services/flowaccount.ts b/src/services/flowaccount.ts
index f434303..a3a02d3 100644
--- a/src/services/flowaccount.ts
+++ b/src/services/flowaccount.ts
@@ -15,6 +15,47 @@ const clientScope = process.env.FLOW_ACCOUNT_CLIENT_SCOPE;
 let token: string = "";
 let tokenExpire: number = Date.now();
 
+enum ContactGroup {
+  PERS = 1,
+  CORP = 3,
+}
+
+enum CreditType {
+  Cash = 3,
+  CreditDay = 1,
+  CreditNoLimit = 5,
+}
+
+enum DocumentDeductionType {
+  Special = 1,
+  Agent = 3,
+  Process = 5,
+  Round = 7,
+}
+
+enum SaleAndPurchaseChannel {
+  Lazada = "Lazada",
+  Shopee = "Shopee",
+}
+
+enum ProductAndServiceType {
+  Service = 1,
+  ProductNonInv = 3,
+  ProductInv = 5,
+}
+
+type ProductAndService = {
+  type?: ProductAndServiceType;
+  name: string;
+  description?: string;
+  quantity: number;
+  unitName?: string;
+  pricePerUnit: number;
+  total: number;
+  sellChartOfAccountCode?: string;
+  buyChartOfAccountcode?: string;
+};
+
 const flowaccount = {
   auth: async () => {
     // Get new token if it is expiring soon (30s).
@@ -47,6 +88,87 @@ const flowaccount = {
 
     return { token, tokenExpire };
   },
+
+  createInvoice: async (
+    data: {
+      recordId?: string;
+      contactCode?: string;
+      contactName: string;
+      contactAddress: string;
+      contactTaxId?: string;
+      contactBranch?: string;
+      contactPerson?: string;
+      contactEmail?: string;
+      contactNumber?: string;
+      contactZipCode?: string;
+      contactGroup?: ContactGroup;
+      /** This must be in yyyy-MM-dd format if pass as string */
+      publishedOn?: Date | string;
+      creditType?: CreditType;
+      /** This is integer */
+      creditDays?: number;
+      /** This must be in yyyy-MM-dd format if pass as string */
+      dueDate?: Date | string;
+      salesName?: string;
+      projectName?: string;
+      reference?: string;
+      isVatInclusive: boolean;
+      useReceiptDeduction?: boolean;
+      subTotal: number;
+      discounPercentage?: number;
+      discountAmount?: number;
+      totalAfterDiscount: number;
+      isVat?: boolean;
+      vatAmount?: number;
+      /** VAT included */
+      grandTotal?: number;
+      /** แสดงหรือไม่แสดง หัก ณ ที่จ่ายท้ายเอกสาร */
+      documentShowWithholdingTax?: boolean;
+      /** ภาษีหัก ณ ที่จ่าย (%) */
+      documentWithholdingTaxPercentage?: number;
+      /** ภาษีหัก ณ ที่จ่าย */
+      documentWithholdingTaxAmount?: number;
+      documentDeductionType?: DocumentDeductionType;
+      documentDeductionAmount?: number;
+      remarks?: string;
+      internalNotes?: string;
+      showSignatureOrStamp?: boolean;
+      documentStructureType?: "SimpleDocument" | null;
+      saleAndPurchaseChannel?: SaleAndPurchaseChannel;
+      items: ProductAndService[];
+    },
+    withPayment?: boolean,
+  ) => {
+    const { token } = await flowaccount.auth();
+
+    if (data.publishedOn instanceof Date) {
+      let date = data.publishedOn.getDate();
+      let month = data.publishedOn.getMonth() + 1;
+      let year = data.publishedOn.getFullYear();
+      data.publishedOn = `${year}-${String(month).padStart(2, "0")}-${String(date).padStart(2, "0")}`;
+    }
+
+    if (data.dueDate instanceof Date) {
+      let date = data.dueDate.getDate();
+      let month = data.dueDate.getMonth() + 1;
+      let year = data.dueDate.getFullYear();
+      data.dueDate = `${year}-${String(month).padStart(2, "0")}-${String(date).padStart(2, "0")}`;
+    }
+
+    const res = await fetch(api + "/tax-invoices" + withPayment ? "/with-payment" : "", {
+      method: "POST",
+      headers: {
+        ["Content-Type"]: `application/json`,
+        ["Authorization"]: `Bearer ${token}`,
+      },
+      body: JSON.stringify(data),
+    });
+
+    return {
+      status: res.status,
+      body: await res.json(),
+    };
+  },
 };
 
 export default flowaccount;