diff --git a/taxcalc/calculate.py b/taxcalc/calculate.py
index a3604fc68..f99b59791 100644
--- a/taxcalc/calculate.py
+++ b/taxcalc/calculate.py
@@ -191,6 +191,7 @@ def calc_one_year(self, zero_out_calc_vars=False):
         DecomposeEITC(self.policy, self.records)
         IITAX(self.policy, self.records)
         ExpandIncome(self.policy, self.records)
+        FairShareTax(self.policy, self.records)
 
     def calc_all(self, zero_out_calc_vars=False):
         # conducts static analysis of Calculator object for current_year
diff --git a/taxcalc/current_law_policy.json b/taxcalc/current_law_policy.json
index e795f7c7e..8610e1b15 100644
--- a/taxcalc/current_law_policy.json
+++ b/taxcalc/current_law_policy.json
@@ -1977,5 +1977,46 @@
                   [9e99, 9e99, 9e99, 9e99, 9e99, 9e99],
                   [9e99, 9e99, 9e99, 9e99, 9e99, 9e99]],
         "validations": {"min": "_PT_brk6"}
+    },
+    "_FST_AGI_trt":{
+        "long_name": "Rate applied to AGI to determine tentative FST",
+        "description": "The result of multiplying AGI by this is the tentative FST used to calculate final FST",
+        "irs_ref": "",
+        "notes": "",
+        "start_year": 2013,
+        "col_var": "",
+        "row_var": "",
+        "row_label": ["2013"],
+        "cpi_inflated": false,
+        "col_label": "",
+        "value": [0.0]
+     },
+
+    "_FST_AGI_thd_lo":{
+        "long_name": "Minimum AGI needed to be subject to FST",
+        "description": "A taxpayer is only subject to the FST if they exceed this level of AGI",
+        "irs_ref": "",
+        "note": "",
+        "start_year": 2013,
+        "col_var": "",
+        "row_var": "",
+        "row_label": ["2013"],
+        "cpi_inflated": true,
+        "col_label": ["single", "joint", "separate", "head of household", "widow", "separate"],
+        "value": [[1000000, 1000000, 500000, 1000000, 1000000, 500000]]
+    },
+    "_FST_AGI_thd_hi":{
+        "long_name": "AGI level at which the FST is fully phased in",
+        "description": "The FST will be fully phased in at this level of AGI. If there is no phase in, this is equivalent to the lower AGI threshold",
+        "irs_ref": "",
+        "note": "",
+        "start_year": 2013,
+        "col_var": "",
+        "row_var": "",
+        "row_label": ["2013"],
+        "cpi_inflated": true,
+        "col_label": ["single", "joint", "separate", "head of household", "widow", "separate"],
+        "value": [[2000000, 2000000, 1000000, 2000000, 2000000, 1000000]]
+
     }
 }
diff --git a/taxcalc/functions.py b/taxcalc/functions.py
index a7c5738f1..f56e86caf 100644
--- a/taxcalc/functions.py
+++ b/taxcalc/functions.py
@@ -1198,6 +1198,53 @@ def ExpandIncome(ptax_was, e02400, c02500, c00100, e00400, _expanded_income):
     return _expanded_income
 
 
+@iterate_jit(nopython=True)
+def FairShareTax(c00100, _iitax, _combined, ptax_was, ptax_sey, ptax_amc,
+                 MARS, FST_AGI_trt, FST_AGI_thd_lo, FST_AGI_thd_hi,
+                 fst):
+    """
+
+    Parameters
+    ----------
+    c00100: AGI
+    _iitax: Individual income tax
+    _combined: Combined payroll and income tax
+    ptax_was: Payroll tax on wages and salaries
+    ptax_sey: Payroll tax on self-employment income
+    ptax_amc: Additional medicare tax on high earnings
+    MARS: Marital status
+    FST_AGI_trt: Percent of AGI the tentative FST will be. Default = 0.0
+    FST_AGI_thd_lo: Minimum AGI needed to be subject to FST. Default = 500,000
+    for married filling separetly, 1,000,000 for all others.
+    FST_AGI_thd_hi: Level of AGI at which the tax is fully phased in. If
+    equivalent to FST_AGI_thd_lo, the there is no phase in for the tax.
+    Default = 1,000,000 for married filing separetly and 2,000,000 for all
+    others.
+    fst
+
+    Returns
+    -------
+    fst: Fair Share Tax
+
+    """
+    if c00100 >= FST_AGI_thd_lo[MARS - 1]:
+        tentFST = c00100 * FST_AGI_trt
+        employee_share = 0.5 * ptax_was + 0.5 * ptax_sey + ptax_amc
+        if (c00100 >= FST_AGI_thd_hi[MARS - 1] or
+                FST_AGI_thd_hi[MARS - 1] == FST_AGI_thd_lo[MARS - 1]):
+            fst = max(tentFST - _iitax - employee_share, 0.0)
+        else:
+            fst = max((((c00100 - FST_AGI_thd_lo[MARS - 1]) /
+                        (FST_AGI_thd_hi[MARS - 1] -
+                         FST_AGI_thd_lo[MARS - 1])) *
+                       (tentFST - _iitax - employee_share)), 0.0)
+    else:
+        fst = 0.0
+    _iitax += fst
+    _combined += fst
+    return fst, _iitax, _combined
+
+
 def BenefitSurtax(calc):
     """
     BenefitSurtax function: computes itemized-deduction-benefit surtax and
diff --git a/taxcalc/records.py b/taxcalc/records.py
index 4844ca41d..4ce482f81 100644
--- a/taxcalc/records.py
+++ b/taxcalc/records.py
@@ -169,7 +169,7 @@ class instance: Records
         '_iitax', '_refund',
         '_expanded_income', 'c07300',
         'c07600', 'c07240',
-        '_surtax', '_combined', 'personal_credit'])
+        '_surtax', '_combined', 'personal_credit', 'fst'])
 
     INTEGER_CALCULATED_VARS = set([
         '_num', '_sep', '_exact', 'f2555'])