From 119f88e6d20871dffaaf8526dae7ebb35255c41a Mon Sep 17 00:00:00 2001
From: Tarik Gul <47201679+TarikGul@users.noreply.github.com>
Date: Sun, 18 Aug 2024 19:13:50 -0700
Subject: [PATCH] Fix transferable formula (#5956)

* Fix transferable formula

* nits
---
 packages/api-derive/src/balances/all.ts   | 9 +++++++--
 packages/api-derive/src/balances/types.ts | 2 +-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/packages/api-derive/src/balances/all.ts b/packages/api-derive/src/balances/all.ts
index fa69a5cc98..a9224155ce 100644
--- a/packages/api-derive/src/balances/all.ts
+++ b/packages/api-derive/src/balances/all.ts
@@ -57,9 +57,14 @@ function calcShared (api: DeriveApi, bestNumber: BlockNumber, data: DeriveBalanc
   let transferable = null;
 
   if (data.frameSystemAccountInfo?.frozen) {
-    const frozenReserveDiff = data.frameSystemAccountInfo.frozen.sub(data.reservedBalance);
+    const { frameSystemAccountInfo, freeBalance, reservedBalance } = data;
 
-    transferable = api.registry.createType('Balance', allLocked ? 0 : data?.freeBalance.sub(bnMax(frozenReserveDiff, api.consts.balances.existentialDeposit)));
+    transferable = api.registry.createType(
+      'Balance',
+      allLocked
+        ? 0
+        : freeBalance.sub(bnMax(new BN(0), frameSystemAccountInfo.frozen.sub(reservedBalance)))
+    );
   }
 
   return objectSpread({}, data, {
diff --git a/packages/api-derive/src/balances/types.ts b/packages/api-derive/src/balances/types.ts
index aa28324d27..94605cb648 100644
--- a/packages/api-derive/src/balances/types.ts
+++ b/packages/api-derive/src/balances/types.ts
@@ -41,7 +41,7 @@ export interface DeriveBalancesAllAccountData extends DeriveBalancesAccountData
    */
   lockedBreakdown: (PalletBalancesBalanceLock | BalanceLockTo212)[];
   /**
-   * Calculated transferable balance. This uses the formula: free - max(frozen - reserve, ed)
+   * Calculated transferable balance. This uses the formula: free - max(0, frozen - reserve)
    * This is only correct when the return type of `api.query.system.account` is `FrameSystemAccountInfo`.
    * Which is the most up to date calulcation for transferrable balances.
    *