diff --git a/policyengine_us/parameters/gov/irs/deductions/itemized/interest/mortgage/cap.yaml b/policyengine_us/parameters/gov/irs/deductions/itemized/interest/mortgage/cap.yaml
index 2f371e152fd..93db6a454a2 100644
--- a/policyengine_us/parameters/gov/irs/deductions/itemized/interest/mortgage/cap.yaml
+++ b/policyengine_us/parameters/gov/irs/deductions/itemized/interest/mortgage/cap.yaml
@@ -1,14 +1,19 @@
 description: IRS limits the total home mortgage interest deduction to this amount, based on filing status.
 SINGLE:
-  2018-01-01: 1_000_000
+  2017-12-16: 1_000_000
+  2018-01-01: 750_000
 JOINT:
-  2018-01-01: 1_000_000
+  2017-12-16: 1_000_000
+  2018-01-01: 750_000
 SEPARATE:
-  2018-01-01: 500_000
+  2017-12-16: 500_000
+  2018-01-01: 375_000
 HEAD_OF_HOUSEHOLD:
-  2018-01-01: 1_000_000
+  2017-12-16: 1_000_000
+  2018-01-01: 750_000
 SURVIVING_SPOUSE:
-  2018-01-01: 1_000_000
+  2017-12-16: 1_000_000
+  2018-01-01: 750_000
 metadata:
   breakdown: filing_status
   unit: currency-USD
@@ -17,5 +22,7 @@ metadata:
     # Hawaii applies this AGI threshold in the state itemized deductions computation
     - title: Hawaii Income Tax Law, Chapter 235, Section 235-2.4, (j)(3)
       href: https://files.hawaii.gov/tax/legal/hrs/hrs_235.pdf#page=10
-    - title: 26 U.S. Code § 163 - Interest, (h)(3)(F)
+    - title: 26 U.S. Code § 163 - Interest, (h)(3)(F) 
       href: https://www.law.cornell.edu/uscode/text/26/163
+    - title: Tax Cuts and Jobs Act, 131 STAT. 2086, SEC. 11043, (a)(F)(ii)
+      href: https://www.congress.gov/115/statute/STATUTE-131/STATUTE-131-Pg2054.pdf#page=2054
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