diff --git a/packages/account-sdk/src/interface/payment/utils/validation.test.ts b/packages/account-sdk/src/interface/payment/utils/validation.test.ts
index 6f5bb576..07b1e524 100644
--- a/packages/account-sdk/src/interface/payment/utils/validation.test.ts
+++ b/packages/account-sdk/src/interface/payment/utils/validation.test.ts
@@ -13,6 +13,9 @@ describe('validateStringAmount', () => {
 
   it('should reject invalid amounts', () => {
     expect(() => validateStringAmount('0', 6)).toThrow('Invalid amount: must be greater than 0');
+    expect(() => validateStringAmount('00.000000', 6)).toThrow(
+      'Invalid amount: must be greater than 0'
+    );
     expect(() => validateStringAmount('-10', 6)).toThrow('Invalid amount: must be greater than 0');
     expect(() => validateStringAmount('abc', 6)).toThrow('Invalid amount: must be a valid number');
     expect(() => validateStringAmount('10.1234567', 6)).toThrow(
@@ -20,6 +23,15 @@ describe('validateStringAmount', () => {
     );
   });
 
+  it.each(['1abc', '1foo', '1.2.3', '1e6', '1.', '.1', '.', '', ' 1', '1 ', 'Infinity'])(
+    'should reject malformed amount %s',
+    (amount) => {
+      expect(() => validateStringAmount(amount, 6)).toThrow(
+        'Invalid amount: must be a valid number'
+      );
+    }
+  );
+
   it('should reject non-string amounts', () => {
     expect(() => validateStringAmount(10 as any, 6)).toThrow('Invalid amount: must be a string');
   });
diff --git a/packages/account-sdk/src/interface/payment/utils/validation.ts b/packages/account-sdk/src/interface/payment/utils/validation.ts
index c6e2ad7f..33033f42 100644
--- a/packages/account-sdk/src/interface/payment/utils/validation.ts
+++ b/packages/account-sdk/src/interface/payment/utils/validation.ts
@@ -11,13 +11,11 @@ export function validateStringAmount(amount: string, maxDecimals: number): void
     throw new Error('Invalid amount: must be a string');
   }
 
-  const numAmount = parseFloat(amount);
-
-  if (isNaN(numAmount)) {
+  if (!/^-?\d+(?:\.\d+)?$/.test(amount)) {
     throw new Error('Invalid amount: must be a valid number');
   }
 
-  if (numAmount <= 0) {
+  if (amount.startsWith('-') || !/[1-9]/.test(amount)) {
     throw new Error('Invalid amount: must be greater than 0');
   }