diff --git a/packages/middleware-flexible-checksums/src/configuration.ts b/packages/middleware-flexible-checksums/src/configuration.ts
index e92871b491b5..d2dbf210766e 100644
--- a/packages/middleware-flexible-checksums/src/configuration.ts
+++ b/packages/middleware-flexible-checksums/src/configuration.ts
@@ -4,6 +4,7 @@ import {
   Encoder,
   GetAwsChunkedEncodingStream,
   HashConstructor,
+  Provider,
   StreamCollector,
   StreamHasher,
 } from "@smithy/types";
@@ -31,6 +32,11 @@ export interface PreviouslyResolved {
    */
   md5: ChecksumConstructor | HashConstructor;
 
+  /**
+   * Determines when a checksum will be calculated for request payloads
+   */
+  requestChecksumCalculation: Provider<string>;
+
   /**
    * A constructor for a class implementing the {@link Hash} interface that computes SHA1 hashes.
    * @internal
diff --git a/packages/middleware-flexible-checksums/src/flexibleChecksumsMiddleware.spec.ts b/packages/middleware-flexible-checksums/src/flexibleChecksumsMiddleware.spec.ts
index 995ae1db5480..bfc5c4085d6a 100644
--- a/packages/middleware-flexible-checksums/src/flexibleChecksumsMiddleware.spec.ts
+++ b/packages/middleware-flexible-checksums/src/flexibleChecksumsMiddleware.spec.ts
@@ -2,7 +2,7 @@ import { HttpRequest } from "@smithy/protocol-http";
 import { BuildHandlerArguments } from "@smithy/types";
 
 import { PreviouslyResolved } from "./configuration";
-import { ChecksumAlgorithm } from "./constants";
+import { ChecksumAlgorithm, RequestChecksumCalculation } from "./constants";
 import { flexibleChecksumsMiddleware } from "./flexibleChecksumsMiddleware";
 import { getChecksumAlgorithmForRequest } from "./getChecksumAlgorithmForRequest";
 import { getChecksumLocationName } from "./getChecksumLocationName";
@@ -27,7 +27,9 @@ describe(flexibleChecksumsMiddleware.name, () => {
   const mockChecksumLocationName = "mock-checksum-location-name";
 
   const mockInput = {};
-  const mockConfig = {} as PreviouslyResolved;
+  const mockConfig = {
+    requestChecksumCalculation: () => Promise.resolve(RequestChecksumCalculation.WHEN_REQUIRED),
+  } as PreviouslyResolved;
   const mockMiddlewareConfig = { input: mockInput, requestChecksumRequired: false };
 
   const mockBody = { body: "mockRequestBody" };
diff --git a/packages/middleware-flexible-checksums/src/flexibleChecksumsMiddleware.ts b/packages/middleware-flexible-checksums/src/flexibleChecksumsMiddleware.ts
index 5f426f35050c..294b0e7fea8f 100644
--- a/packages/middleware-flexible-checksums/src/flexibleChecksumsMiddleware.ts
+++ b/packages/middleware-flexible-checksums/src/flexibleChecksumsMiddleware.ts
@@ -58,6 +58,7 @@ export const flexibleChecksumsMiddleware =
     const { request } = args;
     const { body: requestBody, headers } = request;
     const { base64Encoder, streamHasher } = config;
+    const requestChecksumCalculation = await config.requestChecksumCalculation();
     const { input, requestChecksumRequired, requestAlgorithmMember } = middlewareConfig;
 
     const checksumAlgorithm = getChecksumAlgorithmForRequest(
@@ -65,6 +66,7 @@ export const flexibleChecksumsMiddleware =
       {
         requestChecksumRequired,
         requestAlgorithmMember,
+        requestChecksumCalculation,
       },
       !!context.isS3ExpressBucket
     );
diff --git a/packages/middleware-flexible-checksums/src/getChecksumAlgorithmForRequest.spec.ts b/packages/middleware-flexible-checksums/src/getChecksumAlgorithmForRequest.spec.ts
index ffefd6efd2b6..5b7998923131 100644
--- a/packages/middleware-flexible-checksums/src/getChecksumAlgorithmForRequest.spec.ts
+++ b/packages/middleware-flexible-checksums/src/getChecksumAlgorithmForRequest.spec.ts
@@ -1,4 +1,4 @@
-import { ChecksumAlgorithm } from "./constants";
+import { DEFAULT_CHECKSUM_ALGORITHM, RequestChecksumCalculation } from "./constants";
 import { getChecksumAlgorithmForRequest } from "./getChecksumAlgorithmForRequest";
 import { CLIENT_SUPPORTED_ALGORITHMS } from "./types";
 
@@ -6,36 +6,88 @@ describe(getChecksumAlgorithmForRequest.name, () => {
   const mockRequestAlgorithmMember = "mockRequestAlgorithmMember";
 
   describe("when requestAlgorithmMember is not provided", () => {
-    it("returns MD5 if requestChecksumRequired is set", () => {
-      expect(getChecksumAlgorithmForRequest({}, { requestChecksumRequired: true })).toEqual(ChecksumAlgorithm.MD5);
+    describe(`when requestChecksumCalculation is '${RequestChecksumCalculation.WHEN_REQUIRED}'`, () => {
+      const mockOptions = { requestChecksumCalculation: RequestChecksumCalculation.WHEN_REQUIRED };
+
+      it(`returns ${DEFAULT_CHECKSUM_ALGORITHM} if requestChecksumRequired is set`, () => {
+        expect(getChecksumAlgorithmForRequest({}, { ...mockOptions, requestChecksumRequired: true })).toEqual(
+          DEFAULT_CHECKSUM_ALGORITHM
+        );
+      });
+
+      it("returns undefined if requestChecksumRequired is false", () => {
+        expect(getChecksumAlgorithmForRequest({}, { ...mockOptions, requestChecksumRequired: false })).toBeUndefined();
+      });
     });
 
-    it("returns undefined if requestChecksumRequired is false", () => {
-      expect(getChecksumAlgorithmForRequest({}, { requestChecksumRequired: false })).toBeUndefined();
+    describe(`when requestChecksumCalculation is '${RequestChecksumCalculation.WHEN_SUPPORTED}'`, () => {
+      const mockOptions = { requestChecksumCalculation: RequestChecksumCalculation.WHEN_SUPPORTED };
+
+      it(`returns ${DEFAULT_CHECKSUM_ALGORITHM} if requestChecksumRequired is set`, () => {
+        expect(getChecksumAlgorithmForRequest({}, { ...mockOptions, requestChecksumRequired: true })).toEqual(
+          DEFAULT_CHECKSUM_ALGORITHM
+        );
+      });
+
+      it(`returns ${DEFAULT_CHECKSUM_ALGORITHM} if requestChecksumRequired is false`, () => {
+        expect(getChecksumAlgorithmForRequest({}, { ...mockOptions, requestChecksumRequired: false })).toEqual(
+          DEFAULT_CHECKSUM_ALGORITHM
+        );
+      });
     });
   });
 
   describe("when requestAlgorithmMember is not set in input", () => {
-    const mockOptions = { requestAlgorithmMember: mockRequestAlgorithmMember };
+    const mockOptionsWithAlgoMember = { requestAlgorithmMember: mockRequestAlgorithmMember };
 
-    it("returns MD5 if requestChecksumRequired is set", () => {
-      expect(getChecksumAlgorithmForRequest({}, { ...mockOptions, requestChecksumRequired: true })).toEqual(
-        ChecksumAlgorithm.MD5
-      );
+    describe(`when requestChecksumCalculation is '${RequestChecksumCalculation.WHEN_REQUIRED}'`, () => {
+      const mockOptions = {
+        ...mockOptionsWithAlgoMember,
+        requestChecksumCalculation: RequestChecksumCalculation.WHEN_REQUIRED,
+      };
+
+      it(`returns ${DEFAULT_CHECKSUM_ALGORITHM} if requestChecksumRequired is set`, () => {
+        expect(getChecksumAlgorithmForRequest({}, { ...mockOptions, requestChecksumRequired: true })).toEqual(
+          DEFAULT_CHECKSUM_ALGORITHM
+        );
+      });
+
+      it("returns undefined if requestChecksumRequired is false", () => {
+        expect(getChecksumAlgorithmForRequest({}, { ...mockOptions, requestChecksumRequired: false })).toBeUndefined();
+      });
     });
 
-    it("returns undefined if requestChecksumRequired is false", () => {
-      expect(getChecksumAlgorithmForRequest({}, { ...mockOptions, requestChecksumRequired: false })).toBeUndefined();
+    describe(`when requestChecksumCalculation is '${RequestChecksumCalculation.WHEN_SUPPORTED}'`, () => {
+      const mockOptions = {
+        ...mockOptionsWithAlgoMember,
+        requestChecksumCalculation: RequestChecksumCalculation.WHEN_SUPPORTED,
+      };
+
+      it(`returns ${DEFAULT_CHECKSUM_ALGORITHM} if requestChecksumRequired is set`, () => {
+        expect(getChecksumAlgorithmForRequest({}, { ...mockOptions, requestChecksumRequired: true })).toEqual(
+          DEFAULT_CHECKSUM_ALGORITHM
+        );
+      });
+
+      it(`returns ${DEFAULT_CHECKSUM_ALGORITHM} if requestChecksumRequired is false`, () => {
+        expect(getChecksumAlgorithmForRequest({}, { ...mockOptions, requestChecksumRequired: false })).toEqual(
+          DEFAULT_CHECKSUM_ALGORITHM
+        );
+      });
     });
   });
 
   it("throws error if input[requestAlgorithmMember] if not supported by client", () => {
     const unsupportedAlgo = "unsupportedAlgo";
     const mockInput = { [mockRequestAlgorithmMember]: unsupportedAlgo };
-    const mockOptions = { requestChecksumRequired: true, requestAlgorithmMember: mockRequestAlgorithmMember };
+    const mockOptions = {
+      requestChecksumRequired: true,
+      requestAlgorithmMember: mockRequestAlgorithmMember,
+      requestChecksumCalculation: RequestChecksumCalculation.WHEN_REQUIRED,
+    };
     expect(() => {
       getChecksumAlgorithmForRequest(mockInput, mockOptions);
-    }).toThrowError(
+    }).toThrow(
       `The checksum algorithm "${unsupportedAlgo}" is not supported by the client.` +
         ` Select one of ${CLIENT_SUPPORTED_ALGORITHMS}.`
     );
@@ -44,7 +96,11 @@ describe(getChecksumAlgorithmForRequest.name, () => {
   describe("returns input[requestAlgorithmMember] if supported by client", () => {
     it.each(CLIENT_SUPPORTED_ALGORITHMS)("Supported algorithm: %s", (supportedAlgorithm) => {
       const mockInput = { [mockRequestAlgorithmMember]: supportedAlgorithm };
-      const mockOptions = { requestChecksumRequired: true, requestAlgorithmMember: mockRequestAlgorithmMember };
+      const mockOptions = {
+        requestChecksumRequired: true,
+        requestAlgorithmMember: mockRequestAlgorithmMember,
+        requestChecksumCalculation: RequestChecksumCalculation.WHEN_REQUIRED,
+      };
       expect(getChecksumAlgorithmForRequest(mockInput, mockOptions)).toEqual(supportedAlgorithm);
     });
   });
diff --git a/packages/middleware-flexible-checksums/src/getChecksumAlgorithmForRequest.ts b/packages/middleware-flexible-checksums/src/getChecksumAlgorithmForRequest.ts
index f3cba4b2313f..78f4568a5c0b 100644
--- a/packages/middleware-flexible-checksums/src/getChecksumAlgorithmForRequest.ts
+++ b/packages/middleware-flexible-checksums/src/getChecksumAlgorithmForRequest.ts
@@ -1,4 +1,9 @@
-import { ChecksumAlgorithm, DEFAULT_CHECKSUM_ALGORITHM, S3_EXPRESS_DEFAULT_CHECKSUM_ALGORITHM } from "./constants";
+import {
+  ChecksumAlgorithm,
+  DEFAULT_CHECKSUM_ALGORITHM,
+  RequestChecksumCalculation,
+  S3_EXPRESS_DEFAULT_CHECKSUM_ALGORITHM,
+} from "./constants";
 import { CLIENT_SUPPORTED_ALGORITHMS } from "./types";
 
 export interface GetChecksumAlgorithmForRequestOptions {
@@ -11,6 +16,11 @@ export interface GetChecksumAlgorithmForRequestOptions {
    * Defines a top-level operation input member that is used to configure request checksum behavior.
    */
   requestAlgorithmMember?: string;
+
+  /**
+   * Determines when a checksum will be calculated for request payloads
+   */
+  requestChecksumCalculation: string;
 }
 
 /**
@@ -20,7 +30,11 @@ export interface GetChecksumAlgorithmForRequestOptions {
  */
 export const getChecksumAlgorithmForRequest = (
   input: any,
-  { requestChecksumRequired, requestAlgorithmMember }: GetChecksumAlgorithmForRequestOptions,
+  {
+    requestChecksumRequired,
+    requestAlgorithmMember,
+    requestChecksumCalculation,
+  }: GetChecksumAlgorithmForRequestOptions,
   isS3Express?: boolean
 ): ChecksumAlgorithm | undefined => {
   const defaultAlgorithm = isS3Express ? S3_EXPRESS_DEFAULT_CHECKSUM_ALGORITHM : DEFAULT_CHECKSUM_ALGORITHM;
@@ -28,8 +42,11 @@ export const getChecksumAlgorithmForRequest = (
   // Either the Operation input member that is used to configure request checksum behavior is not set, or
   // the value for input member to configure flexible checksum is not set.
   if (!requestAlgorithmMember || !input[requestAlgorithmMember]) {
-    // Select an algorithm only if request checksum is required.
-    return requestChecksumRequired ? defaultAlgorithm : undefined;
+    // Select an algorithm only if request checksum calculation is supported
+    // or request checksum is required.
+    return requestChecksumCalculation === RequestChecksumCalculation.WHEN_SUPPORTED || requestChecksumRequired
+      ? defaultAlgorithm
+      : undefined;
   }
 
   const checksumAlgorithm = input[requestAlgorithmMember];