diff --git a/core/base.py b/core/base.py
index c718dc9..131d536 100644
--- a/core/base.py
+++ b/core/base.py
@@ -102,8 +102,6 @@ class SplitPayload(BaseModel):
 
 class CheckPayload(BaseModel):
     proofs: List[Proof]
-    amount: int
-    output_data: MintPayloads
 
 
 class MeltPayload(BaseModel):
diff --git a/mint/app.py b/mint/app.py
index 5aa4318..8610b6b 100644
--- a/mint/app.py
+++ b/mint/app.py
@@ -10,7 +10,7 @@ from fastapi import FastAPI
 from loguru import logger
 
 import core.settings as settings
-from core.base import MintPayloads, SplitPayload, MeltPayload, Proof
+from core.base import MintPayloads, SplitPayload, MeltPayload, CheckPayload
 from core.settings import MINT_PRIVATE_KEY, MINT_SERVER_HOST, MINT_SERVER_PORT
 from lightning import WALLET
 from mint.ledger import Ledger
@@ -144,6 +144,11 @@ async def melt(payload: MeltPayload):
     """
 
 
+@app.post("/check")
+async def check_spendable(payload: CheckPayload):
+    return {"spendable": await ledger.check_spendable(payload.proofs)}
+
+
 @app.post("/split")
 async def split(payload: SplitPayload):
     """
@@ -154,10 +159,14 @@ async def split(payload: SplitPayload):
     amount = payload.amount
     output_data = payload.output_data.blinded_messages
     try:
-        fst_promises, snd_promises = await ledger.split(proofs, amount, output_data)
-        return {"fst": fst_promises, "snd": snd_promises}
+        split_return = await ledger.split(proofs, amount, output_data)
     except Exception as exc:
         return {"error": str(exc)}
+    if not split_return:
+        """There was a problem with the split"""
+        raise Exception("could not split tokens.")
+    fst_promises, snd_promises = split_return
+    return {"fst": fst_promises, "snd": snd_promises}
 
 
 @click.command(
diff --git a/mint/ledger.py b/mint/ledger.py
index caab330..15c43e5 100644
--- a/mint/ledger.py
+++ b/mint/ledger.py
@@ -72,9 +72,13 @@ class Ledger:
         await store_promise(amount, B_x=B_.x, B_y=B_.y, C_x=C_.x, C_y=C_.y, db=self.db)
         return BlindedSignature(amount=amount, C_=BasePoint(x=C_.x, y=C_.y))
 
+    def _check_spendable(self, proof: Proof):
+        """Checks whether the proof was already spent."""
+        return not proof.secret in self.proofs_used
+
     def _verify_proof(self, proof: Proof):
         """Verifies that the proof of promise was issued by this ledger."""
-        if proof.secret in self.proofs_used:
+        if not self._check_spendable(proof):
             raise Exception(f"tokens already spent. Secret: {proof.secret}")
         secret_key = self.keys[proof.amount]  # Get the correct key to check against
         C = Point(proof.C.x, proof.C.y, secp256k1)
@@ -202,8 +206,9 @@ class Ledger:
 
     async def check_spendable(self, proofs: List[Proof]):
         """Checks if all provided proofs are valid and still spendable (i.e. have not been spent)."""
-        if not all([self._verify_proof(p) for p in proofs]):
+        if not all([self._check_spendable(p) for p in proofs]):
             return False
+        return True
 
     async def split(
         self, proofs: List[Proof], amount: int, output_data: List[BlindedMessage]
@@ -211,7 +216,7 @@ class Ledger:
         """Consumes proofs and prepares new promises based on the amount split."""
         self._verify_split_amount(amount)
         # Verify proofs are valid
-        if await self.check_spendable(proofs) == False:
+        if not all([self._verify_proof(p) for p in proofs]):
             return False
 
         total = sum([p["amount"] for p in proofs])
diff --git a/wallet/wallet.py b/wallet/wallet.py
index 543a843..cdfb71d 100644
--- a/wallet/wallet.py
+++ b/wallet/wallet.py
@@ -12,6 +12,7 @@ from core.base import (
     Proof,
     SplitPayload,
     BlindedSignature,
+    CheckPayload,
 )
 from core.db import Database
 from core.split import amount_split
@@ -112,11 +113,15 @@ class LedgerAPI:
 
         return fst_proofs, snd_proofs
 
-    def check_spendable(self, proofs):
-        promises_dict = requests.post(
+    async def check_spendable(self, proofs: List[Proof]):
+        payload = CheckPayload(proofs=proofs)
+        return_dict = requests.post(
             self.url + "/check",
-            json=proofs.dict(),
+            json=payload.dict(),
         ).json()
+        if "spendable" in return_dict and return_dict["spendable"]:
+            return True
+        return False
 
 
 class Wallet(LedgerAPI):
@@ -178,16 +183,12 @@ class Wallet(LedgerAPI):
             await update_proof_reserved(proof, reserved=reserved, db=self.db)
 
     async def check_spendable(self, proofs):
-        await super().check_spendable(proofs)
+        return await super().check_spendable(proofs)
 
     async def invalidate(self, proofs):
         # first we make sure that the server has invalidated these proofs
-        try:
-            await self.split(proofs, sum(p["amount"] for p in proofs))
-        except Exception as exc:
-            assert exc.args[0].startswith("Error: tokens already spent."), Exception(
-                "invalidating unspent tokens"
-            )
+        if await self.check_spendable(proofs):
+            raise Exception("tokens not yet spent.")
 
         # TODO: check with server if they were redeemed already
         for proof in proofs: