diff --git a/src/Concerns/Cash.php b/src/Concerns/Cash.php
index f632e33..efb4e0e 100644
--- a/src/Concerns/Cash.php
+++ b/src/Concerns/Cash.php
@@ -9,6 +9,8 @@ trait Cash
 {
     /**
      * Get formatted amount.
+     * 
+     * @return numeric-string
      */
     public function amount(): string
     {
@@ -17,6 +19,8 @@ public function amount(): string
 
     /**
      * Get formatted cash.
+     * 
+     * @return numeric-string
      */
     public function cashAmount(): string
     {
@@ -27,6 +31,8 @@ public function cashAmount(): string
 
     /**
      * Get amount for cash.
+     * 
+     * @return numeric-string
      */
     public function getCashAmount(): string
     {
@@ -38,7 +44,7 @@ public function getCashAmount(): string
     /**
      * Get closest accepted cash amount.
      *
-     * @param  int|string  $amount
+     * @param  int|numeric-string  $amount
      */
     protected function getClosestAcceptedCashAmount($amount): int
     {
diff --git a/src/Concerns/Gst.php b/src/Concerns/Gst.php
index 8d5bd5a..577ecab 100644
--- a/src/Concerns/Gst.php
+++ b/src/Concerns/Gst.php
@@ -12,7 +12,7 @@ trait Gst
     /**
      * Make object with GST.
      *
-     * @param int|string $amount
+     * @param int|numeric-string $amount
      *
      * @return static
      */
@@ -24,7 +24,7 @@ public static function afterGst($amount)
     /**
      * Make object before applying GST.
      *
-     * @param int|string $amount
+     * @param int|numeric-string $amount
      *
      * @return static
      */
@@ -36,7 +36,7 @@ public static function beforeGst($amount)
     /**
      * Make object without GST.
      *
-     * @param int|string $amount
+     * @param int|numeric-string $amount
      *
      * @return static
      */
diff --git a/src/Concerns/Tax.php b/src/Concerns/Tax.php
index febe942..25494ec 100644
--- a/src/Concerns/Tax.php
+++ b/src/Concerns/Tax.php
@@ -20,7 +20,7 @@ trait Tax
     /**
      * Make object with Tax.
      *
-     * @param int|string $amount
+     * @param int|numeric-string $amount
      * @param \Duit\Contracts\Taxable $taxable
      *
      * @return static
@@ -35,7 +35,7 @@ public static function afterTax($amount, Taxable $taxable)
     /**
      * Make object before applying Tax.
      *
-     * @param int|string $amount
+     * @param int|numeric-string $amount
      * @param \Duit\Contracts\Taxable $taxable
      *
      * @return static
@@ -48,7 +48,7 @@ public static function beforeTax($amount, Taxable $taxable)
     /**
      * Make object without Tax.
      *
-     * @param int|string $amount
+     * @param int|numeric-string $amount
      *
      * @return static
      */
@@ -59,6 +59,8 @@ public static function withoutTax($amount)
 
     /**
      * Get formatted amount with GST.
+     * 
+     * @return numeric-string
      */
     public function amountWithTax(): string
     {
@@ -69,6 +71,8 @@ public function amountWithTax(): string
 
     /**
      * Get formatted cash with GST.
+     * 
+     * @return numeric-string
      */
     public function cashAmountWithTax(): string
     {
@@ -111,6 +115,8 @@ final public function hasTax(): bool
 
     /**
      * Get GST amount.
+     * 
+     * @return numeric-string
      */
     public function getTaxAmount(): string
     {
@@ -123,6 +129,8 @@ public function getTaxAmount(): string
 
     /**
      * Returns the value represented by this object with Tax.
+     * 
+     * @return numeric-string
      */
     public function getAmountWithTax(): string
     {
@@ -135,6 +143,8 @@ public function getAmountWithTax(): string
 
     /**
      * Get amount for cash with Tax.
+     * 
+     * @return numeric-string
      */
     public function getCashAmountWithTax(): string
     {
@@ -146,7 +156,7 @@ public function getCashAmountWithTax(): string
     /**
      * Allocate the money according to a list of ratios with Tax.
      *
-     * @return Money[]
+     * @return array<int, \Money\Money>
      */
     public function allocateWithTax(array $ratios): array
     {
@@ -168,7 +178,7 @@ public function allocateWithTax(array $ratios): array
      * @param int<1, max> $n
      * @throws \InvalidArgumentException If number of targets is not an integer
      *
-     * @return Money[]
+     * @return array<int, \Money\Money>
      */
     public function allocateWithTaxTo(int $n): array
     {
@@ -197,7 +207,7 @@ abstract public function getMoney(): Money;
     /**
      * Build money object.
      *
-     * @param  int|string  $amount
+     * @param  int|numeric-string  $amount
      */
     abstract protected static function asMoney($amount): Money;
 
diff --git a/src/Contracts/Money.php b/src/Contracts/Money.php
index d681fff..571d6de 100644
--- a/src/Contracts/Money.php
+++ b/src/Contracts/Money.php
@@ -6,6 +6,8 @@ interface Money
 {
     /**
      * Returns the value represented by this object.
+     * 
+     * @return numeric-string
      */
     public function getAmount(): string;
 
diff --git a/src/Contracts/Taxable.php b/src/Contracts/Taxable.php
index aa3c795..23874fe 100644
--- a/src/Contracts/Taxable.php
+++ b/src/Contracts/Taxable.php
@@ -8,16 +8,22 @@ interface Taxable
 {
     /**
      * Get tax percentage.
+     * 
+     * @return numeric-string
      */
     public function getAmountWithoutTax(MoneyContract $money): string;
 
     /**
      * Get tax percentage.
+     * 
+     * @return numeric-string
      */
     public function getAmountWithTax(MoneyContract $money): string;
 
     /**
      * Get tax percentage.
+     * 
+     * @return numeric-string
      */
     public function getTaxAmount(MoneyContract $money): string;
 
diff --git a/src/MYR.php b/src/MYR.php
index f814b08..7224bdf 100644
--- a/src/MYR.php
+++ b/src/MYR.php
@@ -32,7 +32,7 @@ class MYR implements Contracts\Money, \JsonSerializable
     /**
      * Construct a new MYR money.
      *
-     * @param int|string $amount
+     * @param int|numeric-string $amount
      */
     public function __construct($amount)
     {
@@ -42,7 +42,7 @@ public function __construct($amount)
     /**
      * Construct a new MYR money.
      *
-     * @param  int|string  $amount
+     * @param  int|numeric-string  $amount
      *
      * @return static
      */
@@ -54,7 +54,7 @@ public static function given($amount)
     /**
      * Parse value as ringgit.
      *
-     * @param  string|array  $value
+     * @param  numeric-string|array  $value
      *
      * @return static
      */
@@ -78,6 +78,8 @@ public static function parse($value)
 
     /**
      * Returns the value represented by this object.
+     * 
+     * @return numeric-string
      */
     public function getAmount(): string
     {
diff --git a/src/Taxable.php b/src/Taxable.php
index 7076886..2cc11f7 100644
--- a/src/Taxable.php
+++ b/src/Taxable.php
@@ -23,6 +23,8 @@ abstract class Taxable implements Contracts\Taxable
 
     /**
      * Get tax percentage.
+     * 
+     * @return numeric-string
      */
     public function getAmountWithoutTax(Money $money): string
     {
@@ -31,6 +33,8 @@ public function getAmountWithoutTax(Money $money): string
 
     /**
      * Get tax percentage.
+     * 
+     * @return numeric-string
      */
     public function getAmountWithTax(Money $money): string
     {
@@ -39,6 +43,8 @@ public function getAmountWithTax(Money $money): string
 
     /**
      * Get tax percentage.
+     * 
+     * @return numeric-string
      */
     public function getTaxAmount(Money $money): string
     {