diff --git a/EvoCalculator.Core.Calculation/v1/Validation.cs b/EvoCalculator.Core.Calculation/v1/Validation.cs
index 9fbbe04..8ac3852 100644
--- a/EvoCalculator.Core.Calculation/v1/Validation.cs
+++ b/EvoCalculator.Core.Calculation/v1/Validation.cs
@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using EvoCalculator.Core.Models.Calculation.Models.Request;
 
 namespace EvoCalculator.Core.Calculation.v1
@@ -33,7 +34,7 @@ namespace EvoCalculator.Core.Calculation.v1
                     "Некорректно указана Дата второго платежа, она не может быть раньше Даты заключения ДЛ");
             }
 
-            if ((preparedValues.FirstPaymentSum / preparedValues.AcceptSum) > 0.5m)
+            if (preparedValues.FirstPaymentSum / preparedValues.AcceptSum >= 0.500001m)
             {
                 errors.Add("Первый платеж по графику более 50% от стоимости ПЛ с учетом скидки. Необходимо уменьшить первый платеж");
             }
diff --git a/EvoCalculator.Core.Tests/Calculation/ValidationTests.cs b/EvoCalculator.Core.Tests/Calculation/ValidationTests.cs
new file mode 100644
index 0000000..750f54e
--- /dev/null
+++ b/EvoCalculator.Core.Tests/Calculation/ValidationTests.cs
@@ -0,0 +1,162 @@
+using System;
+using EvoCalculator.Core.Calculation.v1;
+using EvoCalculator.Core.Models.Calculation.Models.Prepared;
+using EvoCalculator.Core.Models.Calculation.Models.Request;
+using Xunit;
+
+namespace EvoCalculator.Core.Tests.Calculation
+{
+    public class ValidationTests
+    {
+        [Fact]
+        public void ValidationTest1()
+        {
+            var requestCalculation = new RequestCalculation()
+            {
+                preparedValues = new PreparedValues()
+                {
+                    AcceptSum = 791666.6666666667m,
+                    FirstPaymentSum = 395833.3333333334m,
+
+                    Nmper = 5,
+                    IrrExpected = 5,
+                    Discount = 5, ComissionRub = 5,
+                    PaymentDateNew = DateTime.Today.AddDays(1),
+                    DogDate = DateTime.Now,
+                }
+            };
+            var errors = new Validation().ValidatePreparedData(requestCalculation);
+            Assert.Empty(errors);
+        }
+
+        [Fact]
+        public void ValidationTest2()
+        {
+            var requestCalculation = new RequestCalculation()
+            {
+                preparedValues = new PreparedValues()
+                {
+                    AcceptSum = 691666.6666666667m,
+                    FirstPaymentSum = 345833.3333333334m,
+
+                    Nmper = 5,
+                    IrrExpected = 5,
+                    Discount = 5, ComissionRub = 5,
+                    PaymentDateNew = DateTime.Today.AddDays(1),
+                    DogDate = DateTime.Now,
+                }
+            };
+            var errors = new Validation().ValidatePreparedData(requestCalculation);
+            Assert.Empty(errors);
+        }
+
+        [Fact]
+        public void ValidationTest3()
+        {
+            var requestCalculation = new RequestCalculation()
+            {
+                preparedValues = new PreparedValues()
+                {
+                    AcceptSum = 6862036.016666667m,
+                    FirstPaymentSum = 3431018.0083333333m,
+
+                    Nmper = 5,
+                    IrrExpected = 5,
+                    Discount = 5, ComissionRub = 5,
+                    PaymentDateNew = DateTime.Today.AddDays(1),
+                    DogDate = DateTime.Now,
+                }
+            };
+            var errors = new Validation().ValidatePreparedData(requestCalculation);
+            Assert.Empty(errors);
+        }
+
+        [Fact]
+        public void ValidationTest4()
+        {
+            var requestCalculation = new RequestCalculation()
+            {
+                preparedValues = new PreparedValues()
+                {
+                    AcceptSum = 6862036.016666667m,
+                    FirstPaymentSum = 3431024.87036935m,
+
+                    Nmper = 5,
+                    IrrExpected = 5,
+                    Discount = 5, ComissionRub = 5,
+                    PaymentDateNew = DateTime.Today.AddDays(1),
+                    DogDate = DateTime.Now,
+                }
+            };
+
+            var errors = new Validation().ValidatePreparedData(requestCalculation);
+            Assert.Empty(errors);
+        }
+
+        [Fact]
+        public void ValidationTest5()
+        {
+            var requestCalculation = new RequestCalculation()
+            {
+                preparedValues = new PreparedValues()
+                {
+                    AcceptSum = 6862036.016666667m,
+                    FirstPaymentSum = 3499645.23053601m,
+
+                    Nmper = 5,
+                    IrrExpected = 5,
+                    Discount = 5, ComissionRub = 5,
+                    PaymentDateNew = DateTime.Today.AddDays(1),
+                    DogDate = DateTime.Now,
+                }
+            };
+
+            var errors = new Validation().ValidatePreparedData(requestCalculation);
+            Assert.NotEmpty(errors);
+        }
+
+        [Fact]
+        public void ValidationTest6()
+        {
+            var requestCalculation = new RequestCalculation()
+            {
+                preparedValues = new PreparedValues()
+                {
+                    AcceptSum = 6862036.016666667m,
+                    FirstPaymentSum = 3498952.23351869m,
+
+                    Nmper = 5,
+                    IrrExpected = 5,
+                    Discount = 5, ComissionRub = 5,
+                    PaymentDateNew = DateTime.Today.AddDays(1),
+                    DogDate = DateTime.Now,
+                }
+            };
+
+            var errors = new Validation().ValidatePreparedData(requestCalculation);
+            Assert.NotEmpty(errors);
+        }
+
+        [Fact]
+        public void ValidationTest7()
+        {
+            var requestCalculation = new RequestCalculation()
+            {
+                preparedValues = new PreparedValues()
+                {
+                    AcceptSum = 6862036.016666667m,
+                    FirstPaymentSum = 1372407.20333333m,
+
+                    Nmper = 5,
+                    IrrExpected = 5,
+                    Discount = 5, ComissionRub = 5,
+                    PaymentDateNew = DateTime.Today.AddDays(1),
+                    DogDate = DateTime.Now,
+                }
+            };
+
+            var errors = new Validation().ValidatePreparedData(requestCalculation);
+            Assert.Empty(errors);
+        }
+    }
+}
\ No newline at end of file