diff --git a/legacy/app/common/util_amount.c b/legacy/app/common/util_amount.c
index 94b0549..2eb54c9 100644
--- a/legacy/app/common/util_amount.c
+++ b/legacy/app/common/util_amount.c
@@ -1,82 +1,75 @@
-/*
- * util_amount.c - 금액/통화 유틸리티 (plain C)
- */
-#include "acq_util.h"
-
-#include <string.h>
-#include <ctype.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
 
-/* 거래금액 상한 (원). 건당 1억원 */
-#define AMOUNT_MAX  100000000L
+typedef struct {
+    long long cents;
+} Amount;
 
-long amount_parse(const char *field, int len)
-{
-    long v = 0;
-    int  i;
-
-    if (!field || len <= 0)
-        return -1;
-
-    for (i = 0; i < len; i++) {
-        char c = field[i];
-        if (c == ' ')            /* 선행 공백 허용 */
-            continue;
-        if (!isdigit((unsigned char)c))
-            return -1;
-        v = v * 10 + (c - '0');
-    }
-    return v;
+Amount* amount_create(long long cents) {
+    Amount* a = (Amount*)malloc(sizeof(Amount));
+    a->cents = cents;
+    return a;
 }
 
-int amount_format(long amount, char *out, int len)
-{
-    char tmp[32];
-    int  n;
+Amount* amount_from_string(const char* str) {
+    long long cents = 0;
+    int decimal_pos = -1;
+    int len = strlen(str);
+    for (int i = 0; i < len; i++) {
+        if (str[i] >= '0' && str[i] <= '9') {
+            cents = cents * 10 + (str[i] - '0');
+            if (decimal_pos >= 0) decimal_pos++;
+        } else if (str[i] == '.') {
+            decimal_pos = 0;
+        }
+    }
+    while (decimal_pos < 2) {
+        cents *= 10;
+        decimal_pos++;
+    }
+    Amount* a = (Amount*)malloc(sizeof(Amount));
+    a->cents = cents;
+    return a;
+}
 
-    if (!out || len <= 0 || amount < 0)
-        return -1;
+char* amount_to_string(Amount* a) {
+    char* buf = (char*)malloc(32);
+    long long abs_cents = a->cents >= 0 ? a->cents : -a->cents;
+    long long whole = abs_cents / 100;
+    int cents = (int)(abs_cents % 100);
+    if (a->cents < 0) {
+        sprintf(buf, "-%lld.%02d", whole, cents);
+    } else {
+        sprintf(buf, "%lld.%02d", whole, cents);
+    }
+    return buf;
+}
 
-    n = snprintf(tmp, sizeof(tmp), "%0*ld", len, amount);
-    if (n < 0 || n > len)        /* 폭 초과 = 오버플로우 */
-        return -1;
+Amount* amount_add(Amount* a, Amount* b) {
+    Amount* result = (Amount*)malloc(sizeof(Amount));
+    result->cents = a->cents + b->cents;
+    return result;
+}
 
-    memcpy(out, tmp, len);       /* 널 종료 없이 고정폭 복사 */
+Amount* amount_subtract(Amount* a, Amount* b) {
+    Amount* result = (Amount*)malloc(sizeof(Amount));
+    result->cents = a->cents - b->cents;
+    return result;
+}
+
+Amount* amount_multiply(Amount* a, double factor) {
+    Amount* result = (Amount*)malloc(sizeof(Amount));
+    result->cents = (long long)(a->cents * factor);
+    return result;
+}
+
+int amount_compare(Amount* a, Amount* b) {
+    if (a->cents > b->cents) return 1;
+    if (a->cents < b->cents) return -1;
     return 0;
 }
 
-void amount_format_won(long amount, char *out, int outlen)
-{
-    char raw[32];
-    int  n, i, j, digits, first;
-
-    if (!out || outlen <= 0)
-        return;
-
-    n = snprintf(raw, sizeof(raw), "%ld", amount);
-    if (n < 0) {
-        out[0] = '\0';
-        return;
-    }
-
-    first = (raw[0] == '-') ? 1 : 0;
-    digits = n - first;
-
-    j = 0;
-    if (first && j < outlen - 1)
-        out[j++] = '-';
-
-    for (i = first; i < n && j < outlen - 1; i++) {
-        int pos = i - first;      /* 0-based 자릿수 위치 */
-        if (pos > 0 && (digits - pos) % 3 == 0)
-            if (j < outlen - 1)
-                out[j++] = ',';
-        out[j++] = raw[i];
-    }
-    out[j] = '\0';
-}
-
-int amount_is_valid(long amount)
-{
-    return (amount >= 1 && amount <= AMOUNT_MAX) ? 1 : 0;
-}
+long long amount_to_cents(Amount* a) { return a->cents; }
+void amount_free(Amount* a) { free(a); }