diff --git a/app/Models/Credit.php b/app/Models/Credit.php
index 99d3a7eb04..3bf25f801c 100644
--- a/app/Models/Credit.php
+++ b/app/Models/Credit.php
@@ -29,4 +29,9 @@ class Credit extends BaseModel
     {
         return $this->belongsTo(User::class, 'assigned_user_id', 'id');
     }
+
+    public function invoices()
+    {
+        return $this->morphToMany(Invoice::class, 'creditable');
+    }
 }
diff --git a/app/Models/Invoice.php b/app/Models/Invoice.php
index 6d0f178a86..9f01aa01ae 100644
--- a/app/Models/Invoice.php
+++ b/app/Models/Invoice.php
@@ -171,6 +171,12 @@ class Invoice extends BaseModel
         return $this->morphMany(CompanyLedger::class, 'company_ledgerable');
     }
 
+    public function credits()
+    {
+        return $this->morphedByMany(Credit::class, 'creditable')->withPivot('amount');
+    }
+
+
     /* ---------------- */
     /* Settings getters */
     /* ---------------- */
diff --git a/app/Repositories/PaymentRepository.php b/app/Repositories/PaymentRepository.php
index d8ae2f5a26..16fcd186b9 100644
--- a/app/Repositories/PaymentRepository.php
+++ b/app/Repositories/PaymentRepository.php
@@ -31,7 +31,9 @@ class PaymentRepository extends BaseRepository
     }
     
     /**
-     * Saves
+     * Saves a payment.
+     * 
+     * 
      * @param  Request $request the request object
      * @param  Payment $payment The Payment object
      * @return Object       Payment $payment
@@ -41,9 +43,10 @@ class PaymentRepository extends BaseRepository
         //todo this save() only works for new payments... will fail if a Payment is updated and saved through here.
         $payment->fill($request->input());
 
+        $payment->status_id = Payment::STATUS_COMPLETED;
         $payment->save();
         
-        if ($request->input('invoices')) {
+        if ($request->has('invoices')) {
             $invoices = Invoice::whereIn('id', array_column($request->input('invoices'), 'id'))->company()->get();
 
             $payment->invoices()->saveMany($invoices);
@@ -56,7 +59,7 @@ class PaymentRepository extends BaseRepository
                 }
             }
         } else {
-            //paid is made, but not to any invoice, therefore we are applying the payment to the clients credit
+            //payment is made, but not to any invoice, therefore we are applying the payment to the clients credit
             ApplyClientPayment::dispatchNow($payment, $payment->company);
         }
 
@@ -66,4 +69,63 @@ class PaymentRepository extends BaseRepository
 
         return $payment->fresh();
     }
+
+    /**
+     * Updates
+     *
+     * The update code path is different to the save path
+     * additional considerations come into play when 'updating'
+     * a payment.
+     * 
+     * @param  Request $request the request object
+     * @param  Payment $payment The Payment object
+     * @return Object       Payment $payment
+     */
+    public function update(Request $request, Payment $payment) :?Payment
+    {
+        
+        if($payment->amount >= 0)
+            return $this->applyPayment($request, $payment);
+        
+        return $this->refundPayment($request, $payment);
+
+    }
+
+    private function applyPayment(Request $request, Payment $payment) :?Payment
+    {
+
+    }
+
+    private function refundPayment(Request $request, Payment $payment) :?Payment
+    {
+        //temp variable to sum the total refund/credit amount
+        $invoice_total_adjustment = 0;
+
+        if($request->has('invoices')){
+            
+            foreach($request->input('invoices') as $adjusted_invoice) {
+                $invoice = Invoice::whereId($adjusted_invoice['id'])->company()->first();
+                $invoice_total_adjustment += $adjusted_invoice['amount'];
+
+                if(!array_key_exists('credit', $adjusted_invoice)){
+                    //todo - generate Credit Note for $amount on $invoice - the assumption here is that it is a FULL refund
+                }
+
+            }
+
+            if($request->input('amount') != $invoice_total_adjustment)
+                return 'Amount must equal the sum of invoice adjustments';
+        }
+
+
+        //adjust applied amount
+        $payment->applied += $invoice_total_adjustment;
+
+        //adjust clients paid to date
+        $client = $payment->client;
+        $client->paid_to_date += $invoice_total_adjustment;
+    
+    }
+
+    
 }
diff --git a/app/Transformers/ClientContactTransformer.php b/app/Transformers/ClientContactTransformer.php
index 8c7b7edcac..a0de6507a0 100644
--- a/app/Transformers/ClientContactTransformer.php
+++ b/app/Transformers/ClientContactTransformer.php
@@ -43,7 +43,7 @@ class ClientContactTransformer extends EntityTransformer
             'custom_value2' => $contact->custom_value2 ?: '',
             'custom_value3' => $contact->custom_value3 ?: '',
             'custom_value4' => $contact->custom_value4 ?: '',
-            'contact_key' => $contact->contact_key,
+            'contact_key' => $contact->contact_key ?: '',
             'send_invoice' => (bool) $contact->send_invoice,
         ];
     }
diff --git a/database/migrations/2014_10_13_000000_create_users_table.php b/database/migrations/2014_10_13_000000_create_users_table.php
index 3d4411da8b..4a138f622c 100644
--- a/database/migrations/2014_10_13_000000_create_users_table.php
+++ b/database/migrations/2014_10_13_000000_create_users_table.php
@@ -959,6 +959,18 @@ class CreateUsersTable extends Migration
 
         });
 
+
+        Schema::create('creditables', function ($table) { //allows multiple credits to one invoice
+            $table->increments('id');
+            $table->unsignedInteger('credit_id');
+            $table->unsignedInteger('creditable_id');
+            $table->decimal('amount', 16, 4)->default(0);
+            $table->string('creditable_type');
+
+            $table->foreign('credit_id')->references('id')->on('credits')->onDelete('cascade');
+
+        });
+
         Schema::create('payment_libraries', function ($t) {
             $t->increments('id');
             $t->timestamps(6);
diff --git a/database/seeds/RandomDataSeeder.php b/database/seeds/RandomDataSeeder.php
index 4fd1bb0d09..83dbc42a07 100644
--- a/database/seeds/RandomDataSeeder.php
+++ b/database/seeds/RandomDataSeeder.php
@@ -116,6 +116,7 @@ class RandomDataSeeder extends Seeder
             'password' => Hash::make(config('ninja.testvars.password')),
             'email_verified_at' => now(),
             'client_id' =>$client->id,
+            'contact_key' => \Illuminate\Support\Str::random(40),
         ]);