diff --git a/src/vec/base256.h b/src/vec/base256.h
index c385059..1f23f66 100644
--- a/src/vec/base256.h
+++ b/src/vec/base256.h
@@ -115,6 +115,19 @@ class Base256 {
         return *this;
     }
 
+    friend Base256 operator%(const Base256 &rhs, const Base256 &lhs) {
+        Base256 result(rhs);
+        result %= lhs;
+        return result;
+    }
+
+    Base256 &operator%=(const Base256 &rhs) {
+        Base256 remaining;
+        this->div(rhs.data, &remaining.data);
+        this->data = std::move(remaining.data);
+        return *this;
+    }
+
     [[nodiscard]] friend bool operator==(const Base256 &lhs, const Base256 &rhs) {
         return isEqual(lhs.data, rhs.data);
     }
diff --git a/tests/test_base256.cpp b/tests/test_base256.cpp
index cd031e6..b656638 100644
--- a/tests/test_base256.cpp
+++ b/tests/test_base256.cpp
@@ -222,19 +222,16 @@ TEST_CASE("Base256: division by zero (edge cases)") {
     SECTION("Dividing zero by zero yields zero") { REQUIRE(make(0) / make(0) == make(0)); }
 }
 
-// TODO
 TEST_CASE("Base256: remainder / modulo logic") {
     // Assuming you have implemented operator% (e.g., a % b)
     // If not, adapt this to test your exposed remainder API or `div()` method
 
-    /*
     SECTION("Remainder of zero dividend yields zero") {
         // Tests the interior block: `if (remaining != nullptr) *remaining = {0};`
         // when `initialDividendIndex < 0`
         REQUIRE(make(0) % make(123456) == make(0));
     }
 
-
     SECTION("Remainder of division by zero yields zero") {
         // Tests the interior block: `if (remaining != nullptr) *remaining = {0};`
         // when `isZero(divisor)`
@@ -252,7 +249,6 @@ TEST_CASE("Base256: remainder / modulo logic") {
         REQUIRE(make(10) % make(20) == make(10));
         REQUIRE(make(1) % make(MAX_U64) == make(1));
     }
-    */
 }
 
 TEST_CASE("Base256: mixed expressions & combinations") {