diff --git a/l10n_us_hr_payroll/data/state/sc_south_carolina.xml b/l10n_us_hr_payroll/data/state/sc_south_carolina.xml
index 95867646..b2a46192 100644
--- a/l10n_us_hr_payroll/data/state/sc_south_carolina.xml
+++ b/l10n_us_hr_payroll/data/state/sc_south_carolina.xml
@@ -31,8 +31,9 @@
             <field name="rule_parameter_id" ref="rule_parameter_us_sc_suta_rate"/>
             <field name="date_from" eval="datetime(2019, 1, 1).date()"/>
         </record>
+        <!-- Tax rate from https://taxnews.ey.com/news/2019-2183-south-carolina-2020-sui-tax-rates-to-decrease-due-to-elimination-of-the-variable-solvency-surcharge-wage-base-unchanged -->
         <record id="rule_parameter_us_sc_suta_rate_2020" model="hr.rule.parameter.value">
-            <field name="parameter_value">1.09</field>
+            <field name="parameter_value">0.55</field>
             <field name="rule_parameter_id" ref="rule_parameter_us_sc_suta_rate"/>
             <field name="date_from" eval="datetime(2020, 1, 1).date()"/>
         </record>
@@ -56,6 +57,7 @@
             <field name="rule_parameter_id" ref="rule_parameter_us_sc_sit_tax_rate"/>
             <field name="date_from" eval="datetime(2019, 1, 1).date()"/>
         </record>
+        <!-- Substraction Method table from https://dor.sc.gov/forms-site/Forms/WH1603F_2020.pdf-->
         <record id="rule_parameter_us_sc_sit_tax_rate_2020" model="hr.rule.parameter.value">
             <field name="parameter_value">[
                 ( 2620, 0.8,    0.0),
diff --git a/l10n_us_hr_payroll/models/state/sc_south_carolina.py b/l10n_us_hr_payroll/models/state/sc_south_carolina.py
index 169961eb..e877f8f9 100644
--- a/l10n_us_hr_payroll/models/state/sc_south_carolina.py
+++ b/l10n_us_hr_payroll/models/state/sc_south_carolina.py
@@ -24,6 +24,7 @@ def sc_south_carolina_state_income_withholding(payslip, categories, worked_days,
         return 0.0, 0.0
 
     pay_periods = payslip.dict.get_pay_periods_in_year()
+    additional = payslip.contract_id.us_payroll_config_value('state_income_tax_additional_withholding')
     allowances = payslip.contract_id.us_payroll_config_value('sc_w4_sit_allowances')
     tax_rate = payslip.rule_parameter('us_sc_sit_tax_rate')
     personal_exemption = payslip.rule_parameter('us_sc_sit_personal_exemption_rate')
@@ -45,4 +46,5 @@ def sc_south_carolina_state_income_withholding(payslip, categories, worked_days,
             withholding = (taxable_income * (rate / 100.0) - flat_amt)
             break
     withholding /= pay_periods
+    withholding += additional
     return wage, -((withholding / wage) * 100.0)
diff --git a/l10n_us_hr_payroll/tests/test_us_sc_south_carolina_payslip_2020.py b/l10n_us_hr_payroll/tests/test_us_sc_south_carolina_payslip_2020.py
index e17a8052..170c3bf5 100644
--- a/l10n_us_hr_payroll/tests/test_us_sc_south_carolina_payslip_2020.py
+++ b/l10n_us_hr_payroll/tests/test_us_sc_south_carolina_payslip_2020.py
@@ -9,14 +9,15 @@ class TestUsSCPayslip(TestUsPayslip):
     #   2020 Taxes and Rates
     ###
     SC_UNEMP_MAX_WAGE = 14000.0
-    SC_UNEMP = 1.09
+    SC_UNEMP = 0.55
     # Calculation based on https://dor.sc.gov/forms-site/Forms/WH1603F_2020.pdf
 
-    def _test_sit(self, wage, exempt, allowances,  schedule_pay,  date_start, expected_withholding):
+    def _test_sit(self, wage, additional_withholding, exempt, allowances,  schedule_pay,  date_start, expected_withholding):
         employee = self._createEmployee()
         contract = self._createContract(employee,
                                         wage=wage,
                                         state_id=self.get_us_state('SC'),
+                                        state_income_tax_additional_withholding=additional_withholding,
                                         state_income_tax_exempt=exempt,
                                         sc_w4_sit_allowances=allowances,
                                         schedule_pay=schedule_pay)
@@ -25,10 +26,11 @@ class TestUsSCPayslip(TestUsPayslip):
         cats = self._getCategories(payslip)
 
         self._log('Computed period tax: ' + str(expected_withholding))
-        self.assertPayrollEqual(cats.get('EE_US_SIT', 0.0), -expected_withholding)
+        self.assertPayrollAlmostEqual(cats.get('EE_US_SIT', 0.0), -expected_withholding)
 
     def test_2020_taxes_example(self):
         self._test_er_suta('SC', self.SC_UNEMP, date(2020, 1, 1), wage_base=self.SC_UNEMP_MAX_WAGE)
-        self._test_sit(750.0, False, 3.0, 'weekly', date(2020, 1, 1), 28.73)
-        self._test_sit(800.0, True, 0.0, 'weekly', date(2020, 1, 1), 0.00)
-        self._test_sit(9000.0, False, 0.0, 'monthly', date(2020, 1, 1), 594.61)
+        self._test_sit(750.0, 0.0, False, 3.0, 'weekly', date(2020, 1, 1), 28.73)
+        self._test_sit(800.0, 0.0, True, 0.0, 'weekly', date(2020, 1, 1), 0.00)
+        self._test_sit(9000.0, 0.0, False, 0.0, 'monthly', date(2020, 1, 1), 594.61)
+        self._test_sit(5000.0, 10.0, False, 2.0, 'semi-monthly', date(2020, 1, 1), 316.06)
diff --git a/l10n_us_hr_payroll/views/us_payroll_config_views.xml b/l10n_us_hr_payroll/views/us_payroll_config_views.xml
index 8c05dbd3..5a2c6da1 100644
--- a/l10n_us_hr_payroll/views/us_payroll_config_views.xml
+++ b/l10n_us_hr_payroll/views/us_payroll_config_views.xml
@@ -247,6 +247,7 @@
                         <group name="state_sc_south_carolina" string="SC South Carolina" attrs="{'invisible':[('state_id', '!=', %(base.state_us_41)s)]}">
                             <p colspan="2"><h3>Form SC W-4 - State Income Tax</h3></p>
                             <field name="sc_w4_sit_allowances" string="Allowances 5."/>
+                            <field name="state_income_tax_additional_withholding" string="Additional Withholding 6."/>
                             <field name="state_income_tax_exempt" string="Exempt 7."/>
                         </group>
                         <group name="state_sd_south_dakota" string="SD South Dakota" attrs="{'invisible':[('state_id', '!=', %(base.state_us_42)s)]}">