diff --git a/src/addons/qtype/calculated/services/handlers/calculated.ts b/src/addons/qtype/calculated/services/handlers/calculated.ts
index 316372f107f..39e5bdee7e0 100644
--- a/src/addons/qtype/calculated/services/handlers/calculated.ts
+++ b/src/addons/qtype/calculated/services/handlers/calculated.ts
@@ -18,7 +18,7 @@ import { CoreQuestionQuestionParsed, CoreQuestionsAnswers } from '@features/ques
 import { CoreQuestionHandler } from '@features/question/services/question-delegate';
 import { convertTextToHTMLElement } from '@/core/utils/create-html-element';
 import { CoreObject } from '@singletons/object';
-import { makeSingleton } from '@singletons';
+import { makeSingleton, Translate } from '@singletons';
 
 /**
  * Handler to support calculated question type.
@@ -88,7 +88,7 @@ export class AddonQtypeCalculatedHandlerService implements CoreQuestionHandler {
             return -1;
         }
 
-        if (question.parsedSettings.unitdisplay != AddonQtypeCalculatedHandlerService.UNITINPUT && unit) {
+        if (question.parsedSettings.unitdisplay !== AddonQtypeCalculatedHandlerService.UNITINPUT && unit) {
             // There should be no units or be outside of the input, not valid.
             return 0;
         }
@@ -98,8 +98,8 @@ export class AddonQtypeCalculatedHandlerService implements CoreQuestionHandler {
             return 0;
         }
 
-        if (question.parsedSettings.unitdisplay == AddonQtypeCalculatedHandlerService.UNITINPUT &&
-                question.parsedSettings.unitgradingtype == AddonQtypeCalculatedHandlerService.UNITGRADED &&
+        if (question.parsedSettings.unitdisplay === AddonQtypeCalculatedHandlerService.UNITINPUT &&
+                question.parsedSettings.unitgradingtype === AddonQtypeCalculatedHandlerService.UNITGRADED &&
                 !this.isValidValue(unit)) {
             // Unit not supplied inside the input and it's required.
             return 0;
@@ -167,7 +167,7 @@ export class AddonQtypeCalculatedHandlerService implements CoreQuestionHandler {
 
         // If a '.' is present or there are multiple ',' (i.e. 2,456,789) assume ',' is a thousands separator and strip it.
         // Else assume it is a decimal separator, and change it to '.'.
-        if (answer.indexOf('.') != -1 || answer.split(',').length - 1 > 1) {
+        if (answer.indexOf('.') !== -1 || answer.split(',').length - 1 > 1) {
             answer = answer.replace(',', '');
         } else {
             answer = answer.replace(',', '.');
@@ -184,7 +184,7 @@ export class AddonQtypeCalculatedHandlerService implements CoreQuestionHandler {
                 match = answer.match(new RegExp(regexString + '$'));
             }
         } else {
-            unitsLeft = question.parsedSettings.unitsleft == '1';
+            unitsLeft = question.parsedSettings.unitsleft === '1';
             regexString = unitsLeft ? regexString + '$' : '^' + regexString;
 
             match = answer.match(new RegExp(regexString));
@@ -201,6 +201,44 @@ export class AddonQtypeCalculatedHandlerService implements CoreQuestionHandler {
         return { answer: Number(numberString), unit };
     }
 
+    /**
+     * @inheritdoc
+     */
+    getValidationError(
+        question: CoreQuestionQuestionParsed,
+        answers: CoreQuestionsAnswers,
+    ): string | undefined {
+        if (!this.isGradableResponse(question, answers)) {
+            return Translate.instant('addon.qtype_numerical.pleaseenterananswer');
+        }
+
+        const { answer, unit } = this.parseAnswer(question, <string> answers.answer);
+        if (answer === null) {
+            return Translate.instant('addon.qtype_numerica.invalidnumber');
+        }
+
+        if (!question.parsedSettings) {
+            if (this.hasSeparateUnitField(question)) {
+                return Translate.instant('addon.qtype_numerica.unitnotselected');
+            }
+
+            // We cannot know if the answer should contain units or not.
+            return;
+        }
+
+        if (question.parsedSettings.unitdisplay !== AddonQtypeCalculatedHandlerService.UNITINPUT && unit) {
+            return Translate.instant('addon.qtype_numerica.invalidnumbernounit');
+        }
+
+        if (question.parsedSettings.unitdisplay === AddonQtypeCalculatedHandlerService.UNITINPUT &&
+            question.parsedSettings.unitgradingtype === AddonQtypeCalculatedHandlerService.UNITGRADED &&
+            !this.isValidValue(unit)) {
+                return Translate.instant('addon.qtype_numerica.pleaseenteranswerwithoutthousandssep');
+        }
+
+        return;
+    }
+
 }
 
 export const AddonQtypeCalculatedHandler = makeSingleton(AddonQtypeCalculatedHandlerService);
diff --git a/src/addons/qtype/calculatedmulti/services/handlers/calculatedmulti.ts b/src/addons/qtype/calculatedmulti/services/handlers/calculatedmulti.ts
index 3d06667c31f..9ef004135dd 100644
--- a/src/addons/qtype/calculatedmulti/services/handlers/calculatedmulti.ts
+++ b/src/addons/qtype/calculatedmulti/services/handlers/calculatedmulti.ts
@@ -79,6 +79,16 @@ export class AddonQtypeCalculatedMultiHandlerService implements CoreQuestionHand
         return AddonQtypeMultichoiceHandler.isSameResponseSingle(prevAnswers, newAnswers);
     }
 
+    /**
+     * @inheritdoc
+     */
+    getValidationError(
+        question: CoreQuestionQuestionParsed,
+        answers: CoreQuestionsAnswers,
+    ): string | undefined {
+        return AddonQtypeMultichoiceHandler.getValidationError(question, answers);
+    }
+
 }
 
 export const AddonQtypeCalculatedMultiHandler = makeSingleton(AddonQtypeCalculatedMultiHandlerService);
diff --git a/src/addons/qtype/calculatedsimple/services/handlers/calculatedsimple.ts b/src/addons/qtype/calculatedsimple/services/handlers/calculatedsimple.ts
index 787e2d552cf..f4ce213940d 100644
--- a/src/addons/qtype/calculatedsimple/services/handlers/calculatedsimple.ts
+++ b/src/addons/qtype/calculatedsimple/services/handlers/calculatedsimple.ts
@@ -79,6 +79,16 @@ export class AddonQtypeCalculatedSimpleHandlerService implements CoreQuestionHan
         return AddonQtypeCalculatedHandler.isSameResponse(question, prevAnswers, newAnswers);
     }
 
+    /**
+     * @inheritdoc
+     */
+    getValidationError(
+        question: CoreQuestionQuestionParsed,
+        answers: CoreQuestionsAnswers,
+    ): string | undefined {
+        return AddonQtypeCalculatedHandler.getValidationError(question, answers);
+    }
+
 }
 
 export const AddonQtypeCalculatedSimpleHandler = makeSingleton(AddonQtypeCalculatedSimpleHandlerService);
diff --git a/src/addons/qtype/ddimageortext/services/handlers/ddimageortext.ts b/src/addons/qtype/ddimageortext/services/handlers/ddimageortext.ts
index 5729a9fe05e..835dfd37fbf 100644
--- a/src/addons/qtype/ddimageortext/services/handlers/ddimageortext.ts
+++ b/src/addons/qtype/ddimageortext/services/handlers/ddimageortext.ts
@@ -16,7 +16,7 @@ import { Injectable, Type } from '@angular/core';
 
 import { CoreQuestion, CoreQuestionQuestionParsed, CoreQuestionsAnswers } from '@features/question/services/question';
 import { CoreQuestionHandler } from '@features/question/services/question-delegate';
-import { makeSingleton } from '@singletons';
+import { makeSingleton, Translate } from '@singletons';
 
 /**
  * Handler to support drag-and-drop onto image question type.
@@ -101,6 +101,20 @@ export class AddonQtypeDdImageOrTextHandlerService implements CoreQuestionHandle
         return CoreQuestion.compareAllAnswers(prevAnswers, newAnswers);
     }
 
+    /**
+     * @inheritdoc
+     */
+    getValidationError(
+        question: CoreQuestionQuestionParsed,
+        answers: CoreQuestionsAnswers,
+    ): string | undefined {
+        if (this.isCompleteResponse(question, answers)) {
+            return;
+        }
+
+        return Translate.instant('addon.qtype_ddimageortext.pleasedraganimagetoeachdropregion');
+    }
+
 }
 
 export const AddonQtypeDdImageOrTextHandler = makeSingleton(AddonQtypeDdImageOrTextHandlerService);
diff --git a/src/addons/qtype/ddmarker/services/handlers/ddmarker.ts b/src/addons/qtype/ddmarker/services/handlers/ddmarker.ts
index 899e0619257..34447ad9257 100644
--- a/src/addons/qtype/ddmarker/services/handlers/ddmarker.ts
+++ b/src/addons/qtype/ddmarker/services/handlers/ddmarker.ts
@@ -18,7 +18,7 @@ import { CoreQuestion, CoreQuestionQuestionParsed, CoreQuestionsAnswers } from '
 import { CoreQuestionHandler } from '@features/question/services/question-delegate';
 import { CoreQuestionHelper, CoreQuestionQuestion } from '@features/question/services/question-helper';
 import { CoreWSFile } from '@services/ws';
-import { makeSingleton } from '@singletons';
+import { makeSingleton, Translate } from '@singletons';
 
 /**
  * Handler to support drag-and-drop markers question type.
@@ -102,7 +102,7 @@ export class AddonQtypeDdMarkerHandlerService implements CoreQuestionHandler {
 
         CoreQuestionHelper.extractQuestionScripts(treatedQuestion, usageId);
 
-        if (treatedQuestion.amdArgs && typeof treatedQuestion.amdArgs[1] == 'string') {
+        if (treatedQuestion.amdArgs && typeof treatedQuestion.amdArgs[1] === 'string') {
             // Moodle 3.6+.
             return [{
                 fileurl: treatedQuestion.amdArgs[1],
@@ -112,6 +112,20 @@ export class AddonQtypeDdMarkerHandlerService implements CoreQuestionHandler {
         return [];
     }
 
+    /**
+     * @inheritdoc
+     */
+    getValidationError(
+        question: CoreQuestionQuestionParsed,
+        answers: CoreQuestionsAnswers,
+    ): string | undefined {
+        if (this.isCompleteResponse(question, answers)) {
+            return;
+        }
+
+        return Translate.instant('addon.qtype_ddmarker.pleasedragatleastonemarker');
+    }
+
 }
 
 export const AddonQtypeDdMarkerHandler = makeSingleton(AddonQtypeDdMarkerHandlerService);
diff --git a/src/addons/qtype/ddwtos/services/handlers/ddwtos.ts b/src/addons/qtype/ddwtos/services/handlers/ddwtos.ts
index f6766968198..67e5acf3802 100644
--- a/src/addons/qtype/ddwtos/services/handlers/ddwtos.ts
+++ b/src/addons/qtype/ddwtos/services/handlers/ddwtos.ts
@@ -12,32 +12,20 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+import { AddonQtypeGapSelectHandlerService } from '@addons/qtype/gapselect/services/handlers/gapselect';
 import { Injectable, Type } from '@angular/core';
 
-import { CoreQuestion, CoreQuestionQuestionParsed, CoreQuestionsAnswers } from '@features/question/services/question';
-import { CoreQuestionHandler } from '@features/question/services/question-delegate';
 import { makeSingleton } from '@singletons';
 
 /**
  * Handler to support drag-and-drop words into sentences question type.
  */
 @Injectable({ providedIn: 'root' })
-export class AddonQtypeDdwtosHandlerService implements CoreQuestionHandler {
+export class AddonQtypeDdwtosHandlerService extends AddonQtypeGapSelectHandlerService {
 
     name = 'AddonQtypeDdwtos';
     type = 'qtype_ddwtos';
 
-    /**
-     * @inheritdoc
-     */
-    getBehaviour(question: CoreQuestionQuestionParsed, behaviour: string): string {
-        if (behaviour === 'interactive') {
-            return 'interactivecountback';
-        }
-
-        return behaviour;
-    }
-
     /**
      * @inheritdoc
      */
@@ -47,58 +35,6 @@ export class AddonQtypeDdwtosHandlerService implements CoreQuestionHandler {
         return AddonQtypeDdwtosComponent;
     }
 
-    /**
-     * @inheritdoc
-     */
-    isCompleteResponse(
-        question: CoreQuestionQuestionParsed,
-        answers: CoreQuestionsAnswers,
-    ): number {
-        for (const name in answers) {
-            const value = answers[name];
-            if (!value || value === '0') {
-                return 0;
-            }
-        }
-
-        return 1;
-    }
-
-    /**
-     * @inheritdoc
-     */
-    async isEnabled(): Promise<boolean> {
-        return true;
-    }
-
-    /**
-     * @inheritdoc
-     */
-    isGradableResponse(
-        question: CoreQuestionQuestionParsed,
-        answers: CoreQuestionsAnswers,
-    ): number {
-        for (const name in answers) {
-            const value = answers[name];
-            if (value && value !== '0') {
-                return 1;
-            }
-        }
-
-        return 0;
-    }
-
-    /**
-     * @inheritdoc
-     */
-    isSameResponse(
-        question: CoreQuestionQuestionParsed,
-        prevAnswers: CoreQuestionsAnswers,
-        newAnswers: CoreQuestionsAnswers,
-    ): boolean {
-        return CoreQuestion.compareAllAnswers(prevAnswers, newAnswers);
-    }
-
 }
 
 export const AddonQtypeDdwtosHandler = makeSingleton(AddonQtypeDdwtosHandlerService);
diff --git a/src/addons/qtype/essay/services/handlers/essay.ts b/src/addons/qtype/essay/services/handlers/essay.ts
index 1ded4f9db73..6833297b354 100644
--- a/src/addons/qtype/essay/services/handlers/essay.ts
+++ b/src/addons/qtype/essay/services/handlers/essay.ts
@@ -84,8 +84,8 @@ export class AddonQtypeEssayHandlerService implements CoreQuestionHandler {
     protected getAllowedOptions(question: CoreQuestionQuestionParsed): { text: boolean; attachments: boolean } {
         if (question.parsedSettings) {
             return {
-                text: question.parsedSettings.responseformat != 'noinline',
-                attachments: question.parsedSettings.attachments != '0',
+                text: question.parsedSettings.responseformat !== 'noinline',
+                attachments: question.parsedSettings.attachments !== '0',
             };
         }
 
@@ -137,6 +137,8 @@ export class AddonQtypeEssayHandlerService implements CoreQuestionHandler {
         question: CoreQuestionQuestionParsed,
         answers: CoreQuestionsAnswers,
         onlineError: string | undefined,
+        component: string,
+        componentId: string | number,
     ): string | undefined {
         if (answers.answer === undefined) {
             // Not answered in offline.
@@ -148,6 +150,10 @@ export class AddonQtypeEssayHandlerService implements CoreQuestionHandler {
             return;
         }
 
+        if (this.isCompleteResponse(question, answers, component, componentId) === 0) {
+            return;
+        }
+
         return this.checkInputWordCount(question, <string> answers.answer, onlineError);
     }
 
@@ -221,7 +227,7 @@ export class AddonQtypeEssayHandlerService implements CoreQuestionHandler {
             return attachments && attachments.length >= Number(question.parsedSettings.attachmentsrequired) ? 1 : 0;
         }
 
-        return ((hasTextAnswer || question.parsedSettings.responserequired == '0') &&
+        return ((hasTextAnswer || question.parsedSettings.responserequired === '0') &&
                 (attachments && attachments.length >= Number(question.parsedSettings.attachmentsrequired))) ? 1 : 0;
     }
 
@@ -452,8 +458,8 @@ export class AddonQtypeEssayHandlerService implements CoreQuestionHandler {
         if (question.isPlainText !== undefined) {
             isPlainText = question.isPlainText;
         } else if (question.parsedSettings) {
-            isPlainText = question.parsedSettings.responseformat == 'monospaced' ||
-                question.parsedSettings.responseformat == 'plain';
+            isPlainText = question.parsedSettings.responseformat === 'monospaced' ||
+                question.parsedSettings.responseformat === 'plain';
         } else {
             const questionEl = convertTextToHTMLElement(question.html);
             isPlainText = !!questionEl.querySelector('.qtype_essay_monospaced') || !!questionEl.querySelector('.qtype_essay_plain');
diff --git a/src/addons/qtype/gapselect/services/handlers/gapselect.ts b/src/addons/qtype/gapselect/services/handlers/gapselect.ts
index 3aa587ccd2c..3c2e3e53070 100644
--- a/src/addons/qtype/gapselect/services/handlers/gapselect.ts
+++ b/src/addons/qtype/gapselect/services/handlers/gapselect.ts
@@ -16,7 +16,7 @@ import { Injectable, Type } from '@angular/core';
 
 import { CoreQuestion, CoreQuestionQuestionParsed, CoreQuestionsAnswers } from '@features/question/services/question';
 import { CoreQuestionHandler } from '@features/question/services/question-delegate';
-import { makeSingleton } from '@singletons';
+import { makeSingleton, Translate } from '@singletons';
 
 /**
  * Handler to support gapselect question type.
@@ -82,7 +82,7 @@ export class AddonQtypeGapSelectHandlerService implements CoreQuestionHandler {
         // We should always get a value for each select so we can assume we receive all the possible answers.
         for (const name in answers) {
             const value = answers[name];
-            if (value) {
+            if (value && value !== '0') {
                 return 1;
             }
         }
@@ -101,6 +101,20 @@ export class AddonQtypeGapSelectHandlerService implements CoreQuestionHandler {
         return CoreQuestion.compareAllAnswers(prevAnswers, newAnswers);
     }
 
+    /**
+     * @inheritdoc
+     */
+    getValidationError(
+        question: CoreQuestionQuestionParsed,
+        answers: CoreQuestionsAnswers,
+    ): string | undefined {
+        if (this.isCompleteResponse(question, answers)) {
+            return;
+        }
+
+        return Translate.instant('addon.qtype_gapselect.pleaseputananswerineachbox');
+    }
+
 }
 
 export const AddonQtypeGapSelectHandler = makeSingleton(AddonQtypeGapSelectHandlerService);
diff --git a/src/addons/qtype/match/services/handlers/match.ts b/src/addons/qtype/match/services/handlers/match.ts
index e70ef44fc70..7feb1675a7f 100644
--- a/src/addons/qtype/match/services/handlers/match.ts
+++ b/src/addons/qtype/match/services/handlers/match.ts
@@ -16,7 +16,7 @@ import { Injectable, Type } from '@angular/core';
 
 import { CoreQuestion, CoreQuestionQuestionParsed, CoreQuestionsAnswers } from '@features/question/services/question';
 import { CoreQuestionHandler } from '@features/question/services/question-delegate';
-import { makeSingleton } from '@singletons';
+import { makeSingleton, Translate } from '@singletons';
 
 /**
  * Handler to support match question type.
@@ -101,6 +101,20 @@ export class AddonQtypeMatchHandlerService implements CoreQuestionHandler {
         return CoreQuestion.compareAllAnswers(prevAnswers, newAnswers);
     }
 
+    /**
+     * @inheritdoc
+     */
+    getValidationError(
+        question: CoreQuestionQuestionParsed,
+        answers: CoreQuestionsAnswers,
+    ): string | undefined {
+        if (this.isCompleteResponse(question, answers)) {
+            return;
+        }
+
+        return Translate.instant('addon.qtype_match.pleaseananswerallparts');
+    }
+
 }
 
 export const AddonQtypeMatchHandler = makeSingleton(AddonQtypeMatchHandlerService);
diff --git a/src/addons/qtype/multianswer/services/handlers/multianswer.ts b/src/addons/qtype/multianswer/services/handlers/multianswer.ts
index 322c75d6954..5755722ff7a 100644
--- a/src/addons/qtype/multianswer/services/handlers/multianswer.ts
+++ b/src/addons/qtype/multianswer/services/handlers/multianswer.ts
@@ -17,7 +17,7 @@ import { Injectable, Type } from '@angular/core';
 import { CoreQuestion, CoreQuestionQuestionParsed, CoreQuestionsAnswers } from '@features/question/services/question';
 import { CoreQuestionHandler } from '@features/question/services/question-delegate';
 import { CoreQuestionHelper } from '@features/question/services/question-helper';
-import { makeSingleton } from '@singletons';
+import { makeSingleton, Translate } from '@singletons';
 
 /**
  * Handler to support multianswer question type.
@@ -109,19 +109,34 @@ export class AddonQtypeMultiAnswerHandlerService implements CoreQuestionHandler
      * @inheritdoc
      */
     validateSequenceCheck(question: CoreQuestionQuestionParsed, offlineSequenceCheck: string): boolean {
-        if (question.sequencecheck == Number(offlineSequenceCheck)) {
+        const offlineSequenceCheckNumber = Number(offlineSequenceCheck);
+        if (question.sequencecheck === offlineSequenceCheckNumber) {
             return true;
         }
 
         // For some reason, viewing a multianswer for the first time without answering it creates a new step "todo".
         // We'll treat this case as valid.
-        if (question.sequencecheck == 2 && question.state == 'todo' && offlineSequenceCheck == '1') {
+        if (question.sequencecheck === 2 && question.state === 'todo' && offlineSequenceCheckNumber === 1) {
             return true;
         }
 
         return false;
     }
 
+    /**
+     * @inheritdoc
+     */
+    getValidationError(
+        question: CoreQuestionQuestionParsed,
+        answers: CoreQuestionsAnswers,
+    ): string | undefined {
+        if (this.isCompleteResponse(question, answers)) {
+            return;
+        }
+
+        return Translate.instant('addon.qtype_multianswer.pleaseananswerallparts');
+    }
+
 }
 
 export const AddonQtypeMultiAnswerHandler = makeSingleton(AddonQtypeMultiAnswerHandlerService);
diff --git a/src/addons/qtype/multichoice/services/handlers/multichoice.ts b/src/addons/qtype/multichoice/services/handlers/multichoice.ts
index 9a02f2e2fd4..09372f7b1a1 100644
--- a/src/addons/qtype/multichoice/services/handlers/multichoice.ts
+++ b/src/addons/qtype/multichoice/services/handlers/multichoice.ts
@@ -18,7 +18,7 @@ import { AddonModQuizMultichoiceQuestion } from '@features/question/classes/base
 import { CoreQuestionQuestionParsed, CoreQuestionsAnswers } from '@features/question/services/question';
 import { CoreQuestionHandler } from '@features/question/services/question-delegate';
 import { CoreObject } from '@singletons/object';
-import { makeSingleton } from '@singletons';
+import { makeSingleton, Translate } from '@singletons';
 
 /**
  * Handler to support multichoice question type.
@@ -50,7 +50,7 @@ export class AddonQtypeMultichoiceHandlerService implements CoreQuestionHandler
 
         // To know if it's single or multi answer we need to search for answers with "choice" in the name.
         for (const name in answers) {
-            if (name.indexOf('choice') != -1) {
+            if (name.indexOf('choice') !== -1) {
                 isSingle = false;
                 if (answers[name]) {
                     isMultiComplete = true;
@@ -160,6 +160,22 @@ export class AddonQtypeMultichoiceHandlerService implements CoreQuestionHandler
         }
     }
 
+    /**
+     * @inheritdoc
+     */
+    getValidationError(
+        question: AddonModQuizMultichoiceQuestion,
+        answers: CoreQuestionsAnswers,
+    ): string | undefined {
+        if (this.isGradableResponse(question, answers)) {
+            return '';
+        }
+
+        return question.multi
+            ? Translate.instant('addon.qtype_multichoice.pleaseselectatleastoneanswer')
+            : Translate.instant('addon.qtype_multichoice.pleaseselectananswer');
+    }
+
 }
 
 export const AddonQtypeMultichoiceHandler = makeSingleton(AddonQtypeMultichoiceHandlerService);
diff --git a/src/addons/qtype/shortanswer/services/handlers/shortanswer.ts b/src/addons/qtype/shortanswer/services/handlers/shortanswer.ts
index 1f34de4ded5..3055ff458ca 100644
--- a/src/addons/qtype/shortanswer/services/handlers/shortanswer.ts
+++ b/src/addons/qtype/shortanswer/services/handlers/shortanswer.ts
@@ -17,7 +17,7 @@ import { Injectable, Type } from '@angular/core';
 import { CoreQuestionQuestionParsed, CoreQuestionsAnswers } from '@features/question/services/question';
 import { CoreQuestionHandler } from '@features/question/services/question-delegate';
 import { CoreObject } from '@singletons/object';
-import { makeSingleton } from '@singletons';
+import { makeSingleton, Translate } from '@singletons';
 
 /**
  * Handler to support short answer question type.
@@ -75,6 +75,20 @@ export class AddonQtypeShortAnswerHandlerService implements CoreQuestionHandler
         return CoreObject.sameAtKeyMissingIsBlank(prevAnswers, newAnswers, 'answer');
     }
 
+    /**
+     * @inheritdoc
+     */
+    getValidationError(
+        question: CoreQuestionQuestionParsed,
+        answers: CoreQuestionsAnswers,
+    ): string | undefined {
+        if (this.isGradableResponse(question, answers)) {
+            return;
+        }
+
+        return Translate.instant('addon.qtype_shortanswer.pleaseenterananswer');
+    }
+
 }
 
 export const AddonQtypeShortAnswerHandler = makeSingleton(AddonQtypeShortAnswerHandlerService);
diff --git a/src/addons/qtype/truefalse/services/handlers/truefalse.ts b/src/addons/qtype/truefalse/services/handlers/truefalse.ts
index 7e1b7bd03cd..24a05d9de16 100644
--- a/src/addons/qtype/truefalse/services/handlers/truefalse.ts
+++ b/src/addons/qtype/truefalse/services/handlers/truefalse.ts
@@ -18,7 +18,7 @@ import { CoreQuestionHandler } from '@features/question/services/question-delega
 import { CoreQuestionQuestionParsed, CoreQuestionsAnswers } from '@features/question/services/question';
 import { CoreObject } from '@singletons/object';
 import { AddonModQuizMultichoiceQuestion } from '@features/question/classes/base-question-component';
-import { makeSingleton } from '@singletons';
+import { makeSingleton, Translate } from '@singletons';
 
 /**
  * Handler to support true/false question type.
@@ -90,6 +90,20 @@ export class AddonQtypeTrueFalseHandlerService implements CoreQuestionHandler {
         }
     }
 
+    /**
+     * @inheritdoc
+     */
+    getValidationError(
+        question: CoreQuestionQuestionParsed,
+        answers: CoreQuestionsAnswers,
+    ): string | undefined {
+        if (this.isGradableResponse(question, answers)) {
+            return;
+        }
+
+        return Translate.instant('addon.qtype_truefalse.pleaseselectananswer');
+    }
+
 }
 
 export const AddonQtypeTrueFalseHandler = makeSingleton(AddonQtypeTrueFalseHandlerService);
diff --git a/src/core/features/question/services/question-delegate.ts b/src/core/features/question/services/question-delegate.ts
index a1e374e5f0a..7d9b2bece74 100644
--- a/src/core/features/question/services/question-delegate.ts
+++ b/src/core/features/question/services/question-delegate.ts
@@ -59,6 +59,8 @@ export interface CoreQuestionHandler extends CoreDelegateHandler {
 
     /**
      * Check if there's a validation error with the offline data.
+     * In situations where isGradableResponse returns false, this method
+     * should generate a description of what the problem is.
      *
      * @param question The question.
      * @param answers Object with the question offline answers (without prefix).