diff --git a/src/proposals/dto/create-measurement-period.dto.ts b/src/proposals/dto/create-measurement-period.dto.ts
index 03a9a75d2..f5e4638b8 100644
--- a/src/proposals/dto/create-measurement-period.dto.ts
+++ b/src/proposals/dto/create-measurement-period.dto.ts
@@ -2,6 +2,15 @@ import { ApiProperty } from "@nestjs/swagger";
 import { IsDateString, IsOptional, IsString } from "class-validator";
 
 export class CreateMeasurementPeriodDto {
+  @ApiProperty({
+    type: String,
+    description:
+      "Unique identifier (relative to the proposal) of a MeasurementPeriod",
+  })
+  @IsString()
+  @IsOptional()
+  id?: string;
+
   @ApiProperty({
     type: String,
     required: true,
diff --git a/src/proposals/dto/update-proposal.dto.ts b/src/proposals/dto/update-proposal.dto.ts
index 1ce6ce0f8..2c23064a9 100644
--- a/src/proposals/dto/update-proposal.dto.ts
+++ b/src/proposals/dto/update-proposal.dto.ts
@@ -7,10 +7,12 @@ import {
   IsObject,
   IsOptional,
   IsString,
+  Validate,
   ValidateNested,
 } from "class-validator";
 import { OwnableDto } from "../../common/dto/ownable.dto";
 import { CreateMeasurementPeriodDto } from "./create-measurement-period.dto";
+import { UniqueMeasurementPeriodIdConstraint } from "./validators/unique-measurement-period-id";
 
 @ApiTags("proposals")
 export class UpdateProposalDto extends OwnableDto {
@@ -113,6 +115,7 @@ export class UpdateProposalDto extends OwnableDto {
   @IsOptional()
   @ValidateNested({ each: true })
   @Type(() => CreateMeasurementPeriodDto)
+  @Validate(UniqueMeasurementPeriodIdConstraint)
   readonly MeasurementPeriodList?: CreateMeasurementPeriodDto[];
 
   @ApiProperty({
diff --git a/src/proposals/dto/validators/unique-measurement-period-id.ts b/src/proposals/dto/validators/unique-measurement-period-id.ts
new file mode 100644
index 000000000..0aa85d6a6
--- /dev/null
+++ b/src/proposals/dto/validators/unique-measurement-period-id.ts
@@ -0,0 +1,23 @@
+import {
+  ValidationArguments,
+  ValidatorConstraint,
+  ValidatorConstraintInterface,
+} from "class-validator";
+import { MeasurementPeriodClass } from "src/proposals/schemas/measurement-period.schema";
+
+@ValidatorConstraint({ async: false })
+export class UniqueMeasurementPeriodIdConstraint
+  implements ValidatorConstraintInterface
+{
+  validate(
+    measurementPeriods: MeasurementPeriodClass[],
+    args: ValidationArguments,
+  ) {
+    const ids = measurementPeriods.map((period) => period.id);
+    return ids.length === new Set(ids).size;
+  }
+
+  defaultMessage(args: ValidationArguments) {
+    return "MeasurementPeriod id must be unique within the MeasurementPeriodList";
+  }
+}
diff --git a/src/proposals/schemas/measurement-period.schema.ts b/src/proposals/schemas/measurement-period.schema.ts
index 3ccd6df18..8dc1b5fee 100644
--- a/src/proposals/schemas/measurement-period.schema.ts
+++ b/src/proposals/schemas/measurement-period.schema.ts
@@ -2,11 +2,26 @@ import { Prop, Schema, SchemaFactory } from "@nestjs/mongoose";
 import { ApiProperty } from "@nestjs/swagger";
 import { Document } from "mongoose";
 import { QueryableClass } from "src/common/schemas/queryable.schema";
+import { v4 as uuidv4 } from "uuid";
 
 export type MeasurementPeriodDocument = MeasurementPeriodClass & Document;
 
 @Schema()
 export class MeasurementPeriodClass extends QueryableClass {
+  @ApiProperty({
+    type: String,
+    default: () => uuidv4(),
+    required: true,
+    description:
+      "Unique identifier (relative to the proposal) of a MeasurementPeriod",
+  })
+  @Prop({
+    type: String,
+    required: true,
+    default: () => uuidv4(),
+  })
+  id: string;
+
   @ApiProperty({
     type: String,
     required: true,
diff --git a/src/proposals/schemas/proposal.schema.ts b/src/proposals/schemas/proposal.schema.ts
index 8e26a1692..d58eeccd7 100644
--- a/src/proposals/schemas/proposal.schema.ts
+++ b/src/proposals/schemas/proposal.schema.ts
@@ -156,6 +156,16 @@ export class ProposalClass extends OwnableClass {
   @Prop({
     type: [MeasurementPeriodSchema],
     required: false,
+    validate: {
+      validator: function (measurementPeriodList: MeasurementPeriodClass[]) {
+        const ids = measurementPeriodList.map(
+          (measurementPeriod) => measurementPeriod.id,
+        );
+        return ids.length === new Set(ids).size;
+      },
+      message:
+        "MeasurementPeriod id must be unique within the MeasurementPeriodList",
+    },
   })
   MeasurementPeriodList?: MeasurementPeriodClass[];
 
diff --git a/test/Proposal.js b/test/Proposal.js
index 411aa220f..0270898c3 100644
--- a/test/Proposal.js
+++ b/test/Proposal.js
@@ -163,7 +163,20 @@ describe("1500: Proposal: Simple Proposal", () => {
       });
   });
 
-  it("0080: adds a new complete proposal with an extra field, which should fail", async () => {
+  it("0080: check if complete proposal with two similar MeasurementPeriod.id is valid", async () => {
+    return request(appUrl)
+      .post("/api/v3/Proposals/isValid")
+      .send(TestData.ProposalWrong_2)
+      .set("Accept", "application/json")
+      .set({ Authorization: `Bearer ${accessTokenProposalIngestor}` })
+      .expect(TestData.EntryValidStatusCode)
+      .expect("Content-Type", /json/)
+      .then((res) => {
+        res.body.should.have.property("valid").and.equal(false);
+      });
+  });
+
+  it("0090: adds a new complete proposal with an extra field, which should fail", async () => {
     return request(appUrl)
       .post("/api/v3/Proposals")
       .send(TestData.ProposalWrong_1)
@@ -176,7 +189,7 @@ describe("1500: Proposal: Simple Proposal", () => {
       });
   });
 
-  it("0090: should fetch this new proposal", async () => {
+  it("0100: should fetch this new proposal", async () => {
     return request(appUrl)
       .get("/api/v3/Proposals/" + proposalId)
       .set("Accept", "application/json")
@@ -189,7 +202,7 @@ describe("1500: Proposal: Simple Proposal", () => {
       });
   });
 
-  it("0100: should add a new attachment to this proposal", async () => {
+  it("0110: should add a new attachment to this proposal", async () => {
     let testAttachment = { ...TestData.AttachmentCorrect };
     testAttachment.proposalId = defaultProposalId;
     return request(appUrl)
@@ -220,7 +233,7 @@ describe("1500: Proposal: Simple Proposal", () => {
       });
   });
 
-  it("0110: should fetch this proposal attachment", async () => {
+  it("0120: should fetch this proposal attachment", async () => {
     return request(appUrl)
       .get("/api/v3/Proposals/" + proposalId + "/attachments")
       .set("Accept", "application/json")
@@ -233,7 +246,7 @@ describe("1500: Proposal: Simple Proposal", () => {
       });
   });
 
-  it("0120: should delete this proposal attachment", async () => {
+  it("0130: should delete this proposal attachment", async () => {
     return request(appUrl)
       .delete(
         "/api/v3/Proposals/" + proposalId + "/attachments/" + attachmentId,
@@ -243,7 +256,7 @@ describe("1500: Proposal: Simple Proposal", () => {
       .expect(TestData.SuccessfulDeleteStatusCode);
   });
 
-  it("0130: admin can remove all existing proposals", async () => {
+  it("0140: admin can remove all existing proposals", async () => {
     return await request(appUrl)
       .get("/api/v3/Proposals")
       .set("Accept", "application/json")
diff --git a/test/TestData.js b/test/TestData.js
index f5ca82fbd..9bb08d2a5 100644
--- a/test/TestData.js
+++ b/test/TestData.js
@@ -50,6 +50,7 @@ const TestData = {
     accessGroups: [],
     MeasurementPeriodList: [
       {
+        id: "1",
         instrument: "ESS3-1",
         start: "2017-07-24T13:56:30.000Z",
         end: "2017-07-25T13:56:30.000Z",
@@ -63,6 +64,29 @@ const TestData = {
     ],
   },
 
+  ProposalCorrectComplete2: {
+    proposalId: "20170268",
+    pi_email: "pi@uni.edu",
+    pi_firstname: "principal",
+    pi_lastname: "investigator",
+    email: "proposer@uni.edu",
+    firstname: "proposal",
+    lastname: "proposer",
+    title: "A complete test proposal",
+    abstract: "Abstract of test proposal",
+    ownerGroup: "proposalingestor",
+    accessGroups: [],
+    MeasurementPeriodList: [
+      {
+        id: "1",
+        instrument: "ESS3-1",
+        start: "2017-07-24T13:56:30.000Z",
+        end: "2017-07-25T13:56:30.000Z",
+        comment: "Some comment",
+      }
+    ],
+  },
+
   ProposalWrong_1: {
     proposalId: "20170267",
     pi_email: "pi@uni.edu",
@@ -79,6 +103,35 @@ const TestData = {
     createdBy: "This should not be here",
   },
 
+  ProposalWrong_2: {
+    proposalId: "20170267",
+    pi_email: "pi@uni.edu",
+    pi_firstname: "principal",
+    pi_lastname: "investigator",
+    email: "proposer@uni.edu",
+    firstname: "proposal",
+    lastname: "proposer",
+    title: "A complete test proposal with an extra field",
+    abstract: "Abstract of test proposal",
+    ownerGroup: "20170251-group",
+    accessGroups: [],
+    MeasurementPeriodList: [
+      {
+        id: "1",
+        instrument: "ESS3-1",
+        start: "2017-07-24T13:56:30.000Z",
+        end: "2017-07-25T13:56:30.000Z",
+        comment: "Some comment",
+      },
+      {
+        id: "1",
+        instrument: "ESS3-2",
+        start: "2017-07-28T13:56:30.000Z",
+        end: "2017-07-29T13:56:30.000Z",
+      },
+    ],
+  },
+
   AttachmentCorrect: {
     thumbnail: "data/abc123",
     caption: "Some caption",