Fix rounding issue on refund

.changeset/grumpy-moles-listen.md

@@ -0,0 +1,6 @@
+---
+"@medusajs/core-flows": patch
+"@medusajs/payment": patch
+---
+
+Fix rounding issue on refund creation

packages/core/core-flows/src/payment/workflows/refund-payment.ts

@@ -1,6 +1,8 @@
 import { BigNumberInput, PaymentDTO } from "@medusajs/framework/types"
 import {
   BigNumber,
+  defaultCurrencies,
+  getEpsilonFromDecimalPrecision,
   MathBN,
   MedusaError,
   PaymentEvents,
@@ -78,7 +80,17 @@ export const validateRefundPaymentExceedsCapturedAmountStep = createStep(
 
     const totalRefundedAmount = MathBN.add(refundedAmount, refundAmount)
 
-    if (MathBN.lt(capturedAmount, totalRefundedAmount)) {
+    const upperCurCode = payment.currency_code?.toUpperCase() as string
+    const currencyEpsilon = getEpsilonFromDecimalPrecision(
+      defaultCurrencies[upperCurCode]?.decimal_digits
+    )
+
+    if (
+      MathBN.gte(
+        MathBN.sub(totalRefundedAmount - capturedAmount),
+        currencyEpsilon
+      )
+    ) {
       throw new MedusaError(
         MedusaError.Types.INVALID_DATA,
         `You are not allowed to refund more than the captured amount`

packages/modules/payment/src/services/payment-module.ts

@@ -41,7 +41,9 @@ import {
 } from "@medusajs/framework/types"
 import {
   BigNumber,
+  defaultCurrencies,
   EmitEvents,
+  getEpsilonFromDecimalPrecision,
   InjectManager,
   InjectTransactionManager,
   isPresent,
@@ -878,7 +880,17 @@ export default class PaymentModuleService
 
     const totalRefundedAmount = MathBN.add(refundedAmount, data.amount)
 
-    if (MathBN.lt(capturedAmount, totalRefundedAmount)) {
+    const upperCurCode = payment.currency_code?.toUpperCase() as string
+    const currencyEpsilon = getEpsilonFromDecimalPrecision(
+      defaultCurrencies[upperCurCode]?.decimal_digits
+    )
+
+    if (
+      MathBN.gte(
+        MathBN.sub(totalRefundedAmount - capturedAmount),
+        currencyEpsilon
+      )
+    ) {
       throw new MedusaError(
         MedusaError.Types.INVALID_DATA,
         `You cannot refund more than what is captured on the payment.`