diff --git a/sale_payment_web/models/payment.py b/sale_payment_web/models/payment.py
index 275fbbd5..b205575c 100644
--- a/sale_payment_web/models/payment.py
+++ b/sale_payment_web/models/payment.py
@@ -1,4 +1,4 @@
-from odoo import api, models
+from odoo import api, fields, models
 
 
 class PaymentTransaction(models.Model):
@@ -10,3 +10,9 @@ class PaymentTransaction(models.Model):
         if active_ids and self._context.get('active_model') == 'sale.order':
             values['sale_order_ids'] = [(6, 0, active_ids)]
         return super(PaymentTransaction, self).create(values)
+
+
+class AccountPayment(models.Model):
+    _inherit = 'account.payment'
+
+    sale_order_id = fields.Many2one('sale.order', string="Sale Order")
diff --git a/sale_payment_web/models/sale.py b/sale_payment_web/models/sale.py
index 667c1bcd..eaa7b9fc 100644
--- a/sale_payment_web/models/sale.py
+++ b/sale_payment_web/models/sale.py
@@ -1,9 +1,29 @@
-from odoo import models, _
+from odoo import api, fields, models, _
+from odoo.tools.safe_eval import safe_eval
 
 
 class SaleOrder(models.Model):
     _inherit = 'sale.order'
 
+    manual_payment_ids = fields.One2many('account.payment', 'sale_order_id', string='Manual Payments')
+    manual_amount_registered_payment = fields.Monetary('Manually Registered Amount', compute='_compute_manual_amount_registered_payment')
+    manual_amount_remaining = fields.Monetary('Remaining Amount Due', compute='_compute_manual_amount_registered_payment')
+
+    @api.depends('manual_payment_ids.amount', 'amount_total')
+    def _compute_manual_amount_registered_payment(self):
+        for so in self:
+            so.manual_amount_registered_payment = sum(so.manual_payment_ids.mapped('amount'))
+            so.manual_amount_remaining = so.amount_total - so.manual_amount_registered_payment
+
+
+    def action_manual_payments(self):
+        action = self.env.ref('account.action_account_payments').read()[0]
+        domain = action['domain'] or '[]'
+        domain = safe_eval(domain)
+        domain.append(('id', 'in', self.manual_payment_ids.ids))
+        action['domain'] = domain
+        return action
+
     def action_payment_register(self):
         return {
             'name': _('Register Payment'),
diff --git a/sale_payment_web/tests/test_sale_payment.py b/sale_payment_web/tests/test_sale_payment.py
index e5255f1a..38bd2edf 100644
--- a/sale_payment_web/tests/test_sale_payment.py
+++ b/sale_payment_web/tests/test_sale_payment.py
@@ -1,4 +1,5 @@
 from odoo.addons.sale.tests.test_sale_to_invoice import TestSaleToInvoice
+from odoo.exceptions import UserError
 
 
 class TestSalePayment(TestSaleToInvoice):
@@ -13,6 +14,17 @@ class TestSalePayment(TestSaleToInvoice):
 
     def test_payment(self):
         self.sale_order.action_confirm()
+
+        payment_wizard = self.env['account.payment.register'].with_context(self.context).create({'amount': -15})
+        self.assertTrue(payment_wizard.journal_id)
+        with self.assertRaises(UserError):
+            payment_wizard.create_payments()
+
+        payment_wizard = self.env['account.payment.register'].with_context(self.context).create({'amount': 0})
+        self.assertTrue(payment_wizard.journal_id)
+        with self.assertRaises(UserError):
+            payment_wizard.create_payments()
+
         payment_wizard = self.env['account.payment.register'].with_context(self.context).create({})
         self.assertTrue(payment_wizard.journal_id)
 
@@ -21,3 +33,10 @@ class TestSalePayment(TestSaleToInvoice):
         payment = self.env[payment_action['res_model']].browse(payment_action['res_id'])
         self.assertTrue(payment.exists())
         self.assertEqual(payment.amount, self.sale_order.amount_total)
+
+        self.assertEqual(payment.sale_order_id, self.sale_order)
+
+        payment_wizard = self.env['account.payment.register'].with_context(self.context).create({'amount': 15})
+        self.assertTrue(payment_wizard.journal_id)
+        with self.assertRaises(UserError):
+            payment_wizard.create_payments()
diff --git a/sale_payment_web/views/sale_views.xml b/sale_payment_web/views/sale_views.xml
index b95fdff1..3842dc5b 100644
--- a/sale_payment_web/views/sale_views.xml
+++ b/sale_payment_web/views/sale_views.xml
@@ -7,7 +7,15 @@
         <field name="inherit_id" ref="sale.view_order_form"/>
         <field name="arch" type="xml">
             <xpath expr="//button[@name='action_draft']" position="after">
-                <button name="action_payment_register" type="object" string="Register Payment" />
+                <button name="action_payment_register" type="object" string="Register Payment"/>
+            </xpath>
+            <xpath expr="//field[@name='amount_total']" position="after">
+                <field name="manual_amount_remaining" widget="monetary"/>
+            </xpath>
+            <xpath expr="//div[@name='button_box']" position="inside">
+                <field name="manual_payment_ids" invisible="1"/>
+                <button name="action_manual_payments" string="Manual Payments" type="object" class="oe_stat_button"
+                        icon="fa-dollar" attrs="{'invisible':[('manual_payment_ids', '=', [])]}"/>
             </xpath>
         </field>
     </record>
diff --git a/sale_payment_web/wizard/account_payment_register.py b/sale_payment_web/wizard/account_payment_register.py
index 91dbcc65..53092f00 100644
--- a/sale_payment_web/wizard/account_payment_register.py
+++ b/sale_payment_web/wizard/account_payment_register.py
@@ -5,8 +5,7 @@ from odoo.exceptions import UserError
 class AccountPaymentRegister(models.TransientModel):
     _inherit = 'account.payment.register'
 
-    sale_order_ids = fields.Many2many('sale.order', 'sale_order_payment_rel_transient', 'payment_id', 'sale_order_id',
-                                      string="Sale Orders", copy=False, readonly=True)
+    sale_order_id = fields.Many2one('sale.order', string='Sale Order')
     payment_token_id = fields.Many2one('payment.token', string="Saved payment token",
                                        domain="[('acquirer_id.capture_manually', '=', False), ('company_id', '=', company_id)]",
                                        help="Note that tokens from acquirers set to only authorize transactions "
@@ -16,6 +15,13 @@ class AccountPaymentRegister(models.TransientModel):
 
     currency_id = fields.Many2one(related='journal_id.currency_id')
     amount = fields.Monetary('Amount')
+    so_amount_registered_payment = fields.Monetary(related='sale_order_id.manual_amount_registered_payment')
+    so_amount_remaining = fields.Monetary(related='sale_order_id.manual_amount_remaining')
+    so_amount_over = fields.Boolean()
+
+    @api.onchange('amount')
+    def _compute_amount_remaining(self):
+        self.so_amount_over = self.amount > self.so_amount_remaining
 
     @api.model
     def default_get(self, fields):
@@ -25,26 +31,25 @@ class AccountPaymentRegister(models.TransientModel):
             return super(AccountPaymentRegister, self).default_get(fields)
 
         rec = super(AccountPaymentRegister, self.with_context(active_ids=None)).default_get(fields)
-        sale_orders = self.env['sale.order'].browse(active_ids)
-        company = sale_orders.mapped('company_id')
-        if len(company) != 1:
-            raise UserError('Can only register sale order payments for the sales in the same company.')
-        partner = sale_orders.mapped('partner_id')
-        if len(partner) != 1:
-            raise UserError('Can only register sale order payments for the same customer.')
-        account_receivable = partner.property_account_receivable_id
-        if not account_receivable:
-            raise UserError('Your partner must have an Account Receivable setup.')
-        if 'sale_order_ids' not in rec:
-            rec['sale_order_ids'] = [(6, 0, sale_orders.ids)]
+        sale_order = self.env['sale.order'].browse(active_ids)
+        if len(sale_order) != 1:
+            raise UserError('Register payment must be called on a sale order.')
+
+        if 'sale_order_id' not in rec:
+            rec['sale_order_id'] = sale_order.id
+            rec['so_amount_registered_payment'] = sale_order.manual_amount_registered_payment
+            rec['so_amount_remaining'] = sale_order.manual_amount_remaining
             if 'amount' not in rec:
-                rec['amount'] = sum(sale_orders.mapped('amount_total'))
+                rec['amount'] = sale_order.manual_amount_remaining
         if 'company_id' not in rec:
-            rec['company_id'] = sale_orders[0].company_id.id
+            rec['company_id'] = sale_order.company_id.id
         if 'partner_id' not in rec:
-            rec['partner_id'] = sale_orders[0].partner_id.id
+            rec['partner_id'] = sale_order.partner_id.id
+            account_receivable = sale_order.partner_id.property_account_receivable_id
+            if not account_receivable:
+                raise UserError('Your partner must have an Account Receivable setup.')
         if 'journal_id' not in rec:
-            rec['journal_id'] = self.env['account.journal'].search([('company_id', '=', company.id), ('type', 'in', ('bank', 'cash'))], limit=1).id
+            rec['journal_id'] = self.env['account.journal'].search([('company_id', '=', sale_order.company_id.id), ('type', 'in', ('bank', 'cash'))], limit=1).id
         if 'payment_method_id' not in rec:
             domain = [('payment_type', '=', 'inbound')]
             rec['payment_method_id'] = self.env['account.payment.method'].search(domain, limit=1).id
@@ -65,7 +70,7 @@ class AccountPaymentRegister(models.TransientModel):
         res['domain'] = {'payment_token_id': domain}
         return res
 
-    @api.onchange('journal_id', 'invoice_ids', 'sale_order_ids')
+    @api.onchange('journal_id', 'invoice_ids', 'sale_order_id')
     def _onchange_journal(self):
         active_ids = self._context.get('active_ids')
         if self._context.get('active_model') != 'sale.order' or not active_ids:
@@ -75,50 +80,54 @@ class AccountPaymentRegister(models.TransientModel):
             domain_payment = [('payment_type', '=', 'inbound'), ('id', 'in', journal.inbound_payment_method_ids.ids)]
         return {'domain': {'payment_method_id': domain_payment}}
 
-    def _prepare_communication_sale_orders(self, sale_orders):
-        return " ".join(o.reference or o.name for o in sale_orders)
+    def _prepare_communication_sale_orders(self, sale_order):
+        return " ".join(o.reference or o.name for o in sale_order)
 
-    def _prepare_payment_vals_sale_orders(self, sale_orders):
+    def _prepare_payment_vals_sale_orders(self, sale_order):
         '''Create the payment values.
 
-        :param sale_orders: The sale orders to pay. In case of multiple
+        :param sale_order: The sale orders to pay. In case of multiple
             documents.
         :return: The payment values as a dictionary.
         '''
         if self.amount <= 0:
             raise UserError("You must enter a positive amount.")
+        elif self.amount > self.so_amount_remaining:
+            raise UserError("You cannot make a payment for more than the difference of the total amount and existing "
+                            "payments: %.2f" % self.so_amount_remaining)
         values = {
             'journal_id': self.journal_id.id,
             'payment_method_id': self.payment_method_id.id,
             'payment_date': self.payment_date,
-            'communication': self._prepare_communication_sale_orders(sale_orders),
+            'communication': self._prepare_communication_sale_orders(sale_order),
             # TODO sale orders need to get to transactions somehow
             # 'invoice_ids': [(6, 0, invoices.ids)],
-            'payment_type': 'inbound', #if amount can be negative we need to allow this to be outbound
+            'payment_type': 'inbound',  # if amount can be negative we need to allow this to be outbound
             'amount': self.amount,
-            'currency_id': sale_orders[0].currency_id.id,
-            'partner_id': sale_orders[0].partner_id.id,
+            'currency_id': sale_order.currency_id.id,
+            'partner_id': sale_order.partner_id.id,
             'partner_type': 'customer',
             'payment_token_id': self.payment_token_id.id,
         }
         return values
 
     def get_payments_vals(self):
-        if self.sale_order_ids:
-            return [self._prepare_payment_vals_sale_orders(self.sale_order_ids)]
+        if self.sale_order_id:
+            return [self._prepare_payment_vals_sale_orders(self.sale_order_id)]
         return super(AccountPaymentRegister, self).get_payments_vals()
 
     def create_payments(self):
-        if self.sale_order_ids:
+        if self.sale_order_id:
             # user may not be able to create payment
             res = super(AccountPaymentRegister, self.sudo()).create_payments()
         else:
             res = super(AccountPaymentRegister, self).create_payments()
-        if res and 'res_id' in res and self.sale_order_ids:
+        if res and 'res_id' in res and self.sale_order_id:
             payment = self.env['account.payment'].browse(res['res_id'])
+            self.sale_order_id.manual_payment_ids += payment
             if payment.name:  # if we don't have a name, then it started a transaction and that will be in chatter
                 payment_link = payment._get_payment_chatter_link()
-                for order in self.sale_order_ids:
+                for order in self.sale_order_id:
                     order.message_post(body=_('A %s payment has been registered: %s') % (payment.payment_method_code, payment_link))
             # return a 'dummy' action like object for tests
             return {'res_id': payment.id, 'res_model': payment._name}
diff --git a/sale_payment_web/wizard/account_payment_register_views.xml b/sale_payment_web/wizard/account_payment_register_views.xml
index a5fdba24..02eb97f3 100644
--- a/sale_payment_web/wizard/account_payment_register_views.xml
+++ b/sale_payment_web/wizard/account_payment_register_views.xml
@@ -14,6 +14,14 @@
             <xpath expr="//field[@name='payment_date']" position="after">
                 <field name="currency_id" invisible="True"/>
                 <field name="amount"/>
+                <field name="so_amount_remaining" invisible="1"/>
+                <field name="so_amount_over" invisible="1"/>
+                <div attrs="{'invisible':[('so_amount_over', '=', False)]}" class="text-danger" colspan="4">
+                    <p>
+                        You cannot make a payment for more than the difference of the total amount and existing payments:
+                        <field name="so_amount_remaining"/>
+                    </p>
+                </div>
             </xpath>
         </field>
     </record>