diff --git a/src/food-market.api/Controllers/Sales/RetailSalesController.cs b/src/food-market.api/Controllers/Sales/RetailSalesController.cs
index 35c79f8..6170444 100644
--- a/src/food-market.api/Controllers/Sales/RetailSalesController.cs
+++ b/src/food-market.api/Controllers/Sales/RetailSalesController.cs
@@ -96,7 +96,21 @@ public record RetailSaleInput(
         /// <summary>Sprint 9: код промокода. Если задан — сервер найдёт active-
         /// promotion с этим кодом, проверит период/MinSaleAmount/Scope и
         /// применит скидку (PromotionDiscount/PromotionId/PromotionCode).</summary>
-        string? PromotionCode = null);
+        string? PromotionCode = null,
+        /// <summary>Причина возврата ИНЫМ способом оплаты (не как в исходном чеке).
+        /// Обязательна, когда способ возврата отличается от способа оплаты чека-
+        /// основания; само изменение способа — только с правом администратора.</summary>
+        string? RefundReason = null);
+
+    private static string PaymentLabel(PaymentMethod m) => m switch
+    {
+        PaymentMethod.Cash => "наличные",
+        PaymentMethod.Card => "карта",
+        PaymentMethod.BankTransfer => "перевод",
+        PaymentMethod.Bonus => "бонусы",
+        PaymentMethod.Mixed => "смешанная",
+        _ => m.ToString(),
+    };
 
     public record SalesStatsBucket(DateTime Bucket, decimal Revenue, int Transactions);
 
@@ -315,6 +329,16 @@ public async Task<ActionResult<RetailSaleDto>> Create([FromBody] RetailSaleInput
                 return BadRequest(new { error = "Исходный чек не найден или сам является возвратом.", field = "referenceSaleId" });
             if (refSale.Status != RetailSaleStatus.Posted)
                 return BadRequest(new { error = "Можно возвращать только из проведённого чека.", field = "referenceSaleId" });
+            // Способ возврата по умолчанию = способ оплаты исходного чека (как МойСклад).
+            // Иной способ — только с правом администратора и с указанием причины.
+            if (input.Payment != refSale.Payment)
+            {
+                var isAdmin = User.IsInRole("Admin") || User.IsInRole("SuperAdmin");
+                if (!isAdmin)
+                    return StatusCode(403, new { error = $"Возврат способом «{PaymentLabel(input.Payment)}» отличается от оплаты чека («{PaymentLabel(refSale.Payment)}»). Нужно право администратора.", code = "refund-method-admin" });
+                if (string.IsNullOrWhiteSpace(input.RefundReason))
+                    return BadRequest(new { error = "Укажите причину возврата иным способом оплаты.", field = "refundReason", code = "refund-reason-required" });
+            }
         }
 
         var sale = new RetailSale
@@ -329,7 +353,9 @@ public async Task<ActionResult<RetailSaleDto>> Create([FromBody] RetailSaleInput
             Payment = input.Payment,
             PaidCash = R(input.PaidCash),
             PaidCard = R(input.PaidCard),
-            Notes = input.Notes,
+            Notes = string.IsNullOrWhiteSpace(input.RefundReason)
+                ? input.Notes
+                : $"{input.Notes}{(string.IsNullOrWhiteSpace(input.Notes) ? "" : " · ")}Возврат иным способом: {input.RefundReason.Trim()}".Trim(),
             IsReturn = input.IsReturn,
             ReferenceSaleId = input.IsReturn ? input.ReferenceSaleId : null,
         };
diff --git a/tests/food-market.IntegrationTests/RetailReturnParityTests.cs b/tests/food-market.IntegrationTests/RetailReturnParityTests.cs
new file mode 100644
index 0000000..29286f4
--- /dev/null
+++ b/tests/food-market.IntegrationTests/RetailReturnParityTests.cs
@@ -0,0 +1,77 @@
+using System.Net;
+using System.Net.Http.Json;
+using System.Text.Json;
+using FluentAssertions;
+using foodmarket.IntegrationTests.Support;
+using Xunit;
+
+namespace foodmarket.IntegrationTests;
+
+/// <summary>Паритет возврата покупателя (п.3): способ возврата по умолчанию =
+/// способ оплаты исходного чека; иной способ — только по праву администратора и
+/// с причиной.</summary>
+[Collection(ApiCollection.Name)]
+public class RetailReturnParityTests
+{
+    private readonly ApiFactory _factory;
+    public RetailReturnParityTests(ApiFactory factory) => _factory = factory;
+
+    private static string RandomBarcode()
+        => string.Concat(Enumerable.Range(0, 13).Select(_ => Random.Shared.Next(0, 10)));
+
+    private async Task<(string saleId, string productId, ApiActor.Refs refs)> PostedCashSaleAsync(ApiActor api)
+    {
+        var refs = await api.LoadRefsAsync();
+        var p = await api.CreateProductAsync(refs, $"P-{Guid.NewGuid():N}", 100m, RandomBarcode());
+        // немного остатка
+        var enter = await api.Http.PostAsJsonAsync("/api/inventory/enters", new
+        {
+            date = DateTime.UtcNow, storeId = refs.StoreId, currencyId = refs.CurrencyId,
+            notes = "seed", lines = new[] { new { productId = p, quantity = 10m, unitCost = 50m } },
+        });
+        enter.EnsureSuccessStatusCode();
+        var eid = (await enter.Content.ReadFromJsonAsync<JsonElement>()).GetProperty("id").GetString();
+        (await api.Http.PostAsJsonAsync($"/api/inventory/enters/{eid}/post", new { })).EnsureSuccessStatusCode();
+
+        var sale = await api.Http.PostAsJsonAsync("/api/sales/retail", new
+        {
+            date = DateTime.UtcNow, storeId = refs.StoreId, currencyId = refs.CurrencyId,
+            payment = 0 /*Cash*/, paidCash = 100m, paidCard = 0m, isReturn = false,
+            lines = new[] { new { productId = p, quantity = 1m, unitPrice = 100m, discount = 0m, vatPercent = 12m, sortOrder = 0 } },
+        });
+        sale.StatusCode.Should().Be(HttpStatusCode.Created);
+        var saleId = (await sale.Content.ReadFromJsonAsync<JsonElement>()).GetProperty("id").GetString()!;
+        (await api.Http.PostAsJsonAsync($"/api/sales/retail/{saleId}/post", new { })).EnsureSuccessStatusCode();
+        return (saleId, p, refs);
+    }
+
+    private object ReturnBody(string saleId, string productId, ApiActor.Refs refs, int payment, string? reason)
+        => new
+        {
+            date = DateTime.UtcNow, storeId = refs.StoreId, currencyId = refs.CurrencyId,
+            payment, paidCash = payment == 0 ? 100m : 0m, paidCard = payment == 1 ? 100m : 0m,
+            isReturn = true, referenceSaleId = saleId, refundReason = reason,
+            lines = new[] { new { productId, quantity = 1m, unitPrice = 100m, discount = 0m, vatPercent = 12m, sortOrder = 0 } },
+        };
+
+    [Fact]
+    public async Task Return_same_method_ok_different_method_needs_reason()
+    {
+        var api = new ApiActor(_factory.CreateClient());
+        await api.SignupAndLoginAsync($"ret-{Guid.NewGuid():N}"); // signup-пользователь = Admin
+        var (saleId, p, refs) = await PostedCashSaleAsync(api);
+
+        // Тот же способ (наличные) — ок.
+        var same = await api.Http.PostAsJsonAsync("/api/sales/retail", ReturnBody(saleId, p, refs, 0, null));
+        same.StatusCode.Should().Be(HttpStatusCode.Created, await same.Content.ReadAsStringAsync());
+
+        // Иной способ (карта) без причины — 400 (пользователь-админ проходит проверку права).
+        var noReason = await api.Http.PostAsJsonAsync("/api/sales/retail", ReturnBody(saleId, p, refs, 1, null));
+        noReason.StatusCode.Should().Be(HttpStatusCode.BadRequest);
+        (await noReason.Content.ReadAsStringAsync()).Should().Contain("причину");
+
+        // Иной способ с причиной — ок (админ + причина).
+        var withReason = await api.Http.PostAsJsonAsync("/api/sales/retail", ReturnBody(saleId, p, refs, 1, "покупатель просит на карту"));
+        withReason.StatusCode.Should().Be(HttpStatusCode.Created, await withReason.Content.ReadAsStringAsync());
+    }
+}