diff --git a/ghost/members-api/lib/controllers/RouterController.js b/ghost/members-api/lib/controllers/RouterController.js
index 2e8b4961af..a900bb3314 100644
--- a/ghost/members-api/lib/controllers/RouterController.js
+++ b/ghost/members-api/lib/controllers/RouterController.js
@@ -204,7 +204,6 @@ module.exports = class RouterController {
      * @returns
      */
     async _getSubscriptionCheckoutData(body) {
-        const ghostPriceId = body.priceId;
         const tierId = body.tierId;
         const offerId = body.offerId;
 
@@ -213,33 +212,35 @@ module.exports = class RouterController {
         let offer;
 
         // Validate basic input
-        if (!ghostPriceId && !offerId && !tierId && !cadence) {
+        if (!offerId && !tierId) {
+            logging.error('[RouterController._getSubscriptionCheckoutData] Expected offerId or tierId, received none');
             throw new BadRequestError({
-                message: tpl(messages.badRequest)
+                message: tpl(messages.badRequest),
+                context: 'Expected offerId or tierId, received none'
             });
         }
 
-        if (offerId && (ghostPriceId || (tierId && cadence))) {
+        if (offerId && tierId) {
+            logging.error('[RouterController._getSubscriptionCheckoutData] Expected offerId or tierId, received both');
             throw new BadRequestError({
-                message: tpl(messages.badRequest)
-            });
-        }
-
-        if (ghostPriceId && tierId && cadence) {
-            throw new BadRequestError({
-                message: tpl(messages.badRequest)
+                message: tpl(messages.badRequest),
+                context: 'Expected offerId or tierId, received both'
             });
         }
 
         if (tierId && !cadence) {
+            logging.error('[RouterController._getSubscriptionCheckoutData] Expected cadence to be "month" or "year", received ', cadence);
             throw new BadRequestError({
-                message: tpl(messages.badRequest)
+                message: tpl(messages.badRequest),
+                context: 'Expected cadence to be "month" or "year", received ' + cadence
             });
         }
 
-        if (cadence && cadence !== 'month' && cadence !== 'year') {
+        if (tierId && cadence && cadence !== 'month' && cadence !== 'year') {
+            logging.error('[RouterController._getSubscriptionCheckoutData] Expected cadence to be "month" or "year", received ', cadence);
             throw new BadRequestError({
-                message: tpl(messages.badRequest)
+                message: tpl(messages.badRequest),
+                context: 'Expected cadence to be "month" or "year", received "' + cadence + '"'
             });
         }
 
diff --git a/ghost/members-api/test/unit/lib/controllers/router.test.js b/ghost/members-api/test/unit/lib/controllers/router.test.js
index 3e77a4cd8d..4b54322721 100644
--- a/ghost/members-api/test/unit/lib/controllers/router.test.js
+++ b/ghost/members-api/test/unit/lib/controllers/router.test.js
@@ -1,4 +1,7 @@
 const sinon = require('sinon');
+const assert = require('assert').strict;
+const errors = require('@tryghost/errors');
+
 const RouterController = require('../../../../lib/controllers/RouterController');
 
 describe('RouterController', function () {
@@ -86,6 +89,80 @@ describe('RouterController', function () {
             })).should.be.true();
         });
 
+        describe('_getSubscriptionCheckoutData', function () {
+            it('returns a BadRequestError if both offerId and tierId are missing', async function () {
+                const routerController = new RouterController({
+                    tiersService,
+                    paymentsService,
+                    offersAPI,
+                    stripeAPIService,
+                    labsService
+                });
+
+                try {
+                    await routerController._getSubscriptionCheckoutData({body: {}});
+                    assert.fail('Expected function to throw BadRequestError');
+                } catch (error) {
+                    assert(error instanceof errors.BadRequestError, 'Error should be an instance of BadRequestError');
+                    assert.equal(error.context, 'Expected offerId or tierId, received none');
+                }
+            });
+
+            it('returns a BadRequestError if both offerId and tierId are provided', async function () {
+                const routerController = new RouterController({
+                    tiersService,
+                    paymentsService,
+                    offersAPI,
+                    stripeAPIService,
+                    labsService
+                });
+
+                try {
+                    await routerController._getSubscriptionCheckoutData({tierId: 'tier_123', offerId: 'offer_123'});
+                    assert.fail('Expected function to throw BadRequestError');
+                } catch (error) {
+                    assert(error instanceof errors.BadRequestError, 'Error should be an instance of BadRequestError');
+                    assert.equal(error.context, 'Expected offerId or tierId, received both');
+                }
+            });
+
+            it('returns a BadRequestError if tierId is provided wihout a cadence', async function () {
+                const routerController = new RouterController({
+                    tiersService,
+                    paymentsService,
+                    offersAPI,
+                    stripeAPIService,
+                    labsService
+                });
+
+                try {
+                    await routerController._getSubscriptionCheckoutData({tierId: 'tier_123'});
+                    assert.fail('Expected function to throw BadRequestError');
+                } catch (error) {
+                    assert(error instanceof errors.BadRequestError, 'Error should be an instance of BadRequestError');
+                    assert.equal(error.context, 'Expected cadence to be "month" or "year", received undefined');
+                }
+            });
+
+            it('returns a BadRequestError if tierId is provided wihout a valid cadence', async function () {
+                const routerController = new RouterController({
+                    tiersService,
+                    paymentsService,
+                    offersAPI,
+                    stripeAPIService,
+                    labsService
+                });
+
+                try {
+                    await routerController._getSubscriptionCheckoutData({tierId: 'tier_123', cadence: 'day'});
+                    assert.fail('Expected function to throw BadRequestError');
+                } catch (error) {
+                    assert(error instanceof errors.BadRequestError, 'Error should be an instance of BadRequestError');
+                    assert.equal(error.context, 'Expected cadence to be "month" or "year", received "day"');
+                }
+            });
+        });
+
         afterEach(function () {
             sinon.restore();
         });