diff --git a/backend/grant/proposal/models.py b/backend/grant/proposal/models.py
index 90a481ad..beae8133 100644
--- a/backend/grant/proposal/models.py
+++ b/backend/grant/proposal/models.py
@@ -298,7 +298,15 @@ class Proposal(db.Model):
             if len(milestone.content) > 200:
                 raise ValidationException("Milestone content cannot be longer than 200 chars")
 
-            payout_total += float(milestone.payout_percent)
+            try:
+                p = float(milestone.payout_percent)
+                if p <= 0:
+                    raise ValidationException("Milestone payout percent must be greater than zero")
+
+            except ValueError:
+                raise ValidationException("Milestone payout percent must be a number")
+
+            payout_total += p
 
             try:
                 present = datetime.datetime.today().replace(day=1)
diff --git a/frontend/client/modules/create/utils.ts b/frontend/client/modules/create/utils.ts
index f2963f40..733d2127 100644
--- a/frontend/client/modules/create/utils.ts
+++ b/frontend/client/modules/create/utils.ts
@@ -148,6 +148,10 @@ export function getCreateErrors(
         return 'Payout percent is required';
       } else if (Number.isNaN(parseInt(ms.payoutPercent, 10))) {
         return 'Payout percent must be a valid number';
+      } else if (parseInt(ms.payoutPercent, 10) <= 0) {
+        return 'Payout percent must be greater than zero';
+      } else if (parseInt(ms.payoutPercent, 10) > 100) {
+        return 'Payout percent must be less than or equal to 100';
       }
 
       // Last one shows percentage errors