diff --git a/Gemfile b/Gemfile
index 853db02d..17f26b7c 100644
--- a/Gemfile
+++ b/Gemfile
@@ -69,7 +69,7 @@ gem 'whenever'
 gem 'rqrcode-rails3'
 gem 'exception_notification'
 gem 'rack-canonical-host'
-gem 'bootstrap_forms'
+gem 'bootstrap_forms', github: 'sigmike/bootstrap_forms', branch: 'sanitize_value_in_radio_label_for'
 
 group :test do
   gem 'cucumber-rails', :require => false
diff --git a/Gemfile.lock b/Gemfile.lock
index 9fccff62..c66fe8cd 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -26,6 +26,13 @@ GIT
       rails (>= 3.1)
       railties (>= 3.1)
 
+GIT
+  remote: git://github.com/sigmike/bootstrap_forms.git
+  revision: e69b6834d36b198d36a8f4a892d1bac6633e7545
+  branch: sanitize_value_in_radio_label_for
+  specs:
+    bootstrap_forms (4.0.1)
+
 GEM
   remote: https://rubygems.org/
   specs:
@@ -60,7 +67,6 @@ GEM
     arel (4.0.2)
     atomic (1.1.14)
     bcrypt-ruby (3.1.2)
-    bootstrap_forms (4.0.1)
     builder (3.1.4)
     capistrano (3.0.1)
       i18n
@@ -277,7 +283,7 @@ PLATFORMS
 
 DEPENDENCIES
   airbrake
-  bootstrap_forms
+  bootstrap_forms!
   capistrano (~> 3.0)
   capistrano-bundler (>= 1.1.0)
   capistrano-rails
diff --git a/app/controllers/projects_controller.rb b/app/controllers/projects_controller.rb
index 3bd23bdc..01758224 100644
--- a/app/controllers/projects_controller.rb
+++ b/app/controllers/projects_controller.rb
@@ -28,6 +28,21 @@ def update
     end
   end
 
+  def decide_tip_amounts
+    @project = Project.find params[:id]
+    if request.patch?
+      @project.attributes = params.require(:project).permit(tips_attributes: [:id, :amount_percentage])
+      if @project.save
+        message = "The tip amounts have been defined"
+        if @project.has_undecided_tips?
+          redirect_to decide_tip_amounts_project_path(@project), notice: message
+        else
+          redirect_to @project, notice: message
+        end
+      end
+    end
+  end
+
   def qrcode
     @project = Project.find params[:id]
     respond_to do |format|
diff --git a/app/models/project.rb b/app/models/project.rb
index 251ee04a..50eb2a45 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -1,6 +1,7 @@
 class Project < ActiveRecord::Base
   has_many :deposits # todo: only confirmed deposits that have amount > paid_out
-  has_many :tips
+  has_many :tips, inverse_of: :project
+  accepts_nested_attributes_for :tips
   has_many :collaborators
 
   validates :full_name, uniqueness: true, presence: true
@@ -115,13 +116,7 @@ def tip_for commit
         commit: commit.sha
       })
 
-      # notify user
-      if tip && tip.amount && user.bitcoin_address.blank? && !user.unsubscribed
-        if !user.notified_at || (user.notified_at < (Time.now - 30.days))
-          UserMailer.new_tip(user, tip).deliver
-          user.touch :notified_at
-        end
-      end
+      tip.notify_user
 
       Rails.logger.info "    Tip created #{tip.inspect}"
     end
@@ -185,10 +180,18 @@ def update_info
   end
 
   def tips_to_pay
-    tips.unpaid.with_address
+    tips.to_pay
   end
 
   def amount_to_pay
     tips_to_pay.sum(:amount)
   end
+
+  def has_undecided_tips?
+    tips.undecided.any?
+  end
+
+  def commit_url(commit)
+    "https://github.com/#{full_name}/commit/#{commit}"
+  end
 end
diff --git a/app/models/tip.rb b/app/models/tip.rb
index 63ae2e12..792a4b51 100644
--- a/app/models/tip.rb
+++ b/app/models/tip.rb
@@ -1,14 +1,16 @@
 class Tip < ActiveRecord::Base
   belongs_to :user
   belongs_to :sendmany
-  belongs_to :project
+  belongs_to :project, inverse_of: :tips
 
-  validates :amount, numericality: {greater_than: 0, allow_nil: true}
+  validates :amount, numericality: {greater_or_equal_than: 0, allow_nil: true}
 
   scope :not_sent,      -> { where(sendmany_id: nil) }
 
   scope :unpaid,        -> { non_refunded.not_sent }
 
+  scope :to_pay,        -> { unpaid.decided.with_address }
+
   scope :paid,          -> { where('sendmany_id is not ?', nil) }
 
   scope :refunded,      -> { where('refunded_at is not ?', nil) }
@@ -21,11 +23,16 @@ class Tip < ActiveRecord::Base
 
   scope :with_address,  -> { joins(:user).where('users.bitcoin_address IS NOT NULL AND users.bitcoin_address != ?', "") }
 
+  scope :undecided,     -> { where(amount: nil) }
+  scope :decided,       -> { where.not(amount: nil) }
+
+  after_save :notify_user_if_just_decided
+
   def paid?
     !!sendmany_id
   end
 
-  def amount_undecided?
+  def undecided?
     amount.nil?
   end
 
@@ -36,4 +43,31 @@ def self.refund_unclaimed
       tip.touch :refunded_at
     end
   end
+
+  def commit_url
+    project.commit_url(commit)
+  end
+
+  def amount_percentage
+    nil
+  end
+
+  def amount_percentage=(percentage)
+    if undecided? and percentage.present?
+      self.amount = project.available_amount * (percentage.to_f / 100)
+    end
+  end
+
+  def notify_user
+    if amount and amount > 0 and user.bitcoin_address.blank? and !user.unsubscribed
+      if user.notified_at.nil? or user.notified_at < 30.days.ago
+        UserMailer.new_tip(user, self).deliver
+        user.touch :notified_at
+      end
+    end
+  end
+
+  def notify_user_if_just_decided
+    notify_user if amount_was.nil? and amount
+  end
 end
diff --git a/app/views/projects/decide_tip_amounts.html.haml b/app/views/projects/decide_tip_amounts.html.haml
new file mode 100644
index 00000000..f37d3e70
--- /dev/null
+++ b/app/views/projects/decide_tip_amounts.html.haml
@@ -0,0 +1,25 @@
+= bootstrap_form_for @project, url: decide_tip_amounts_project_path(@project) do |f|
+  %table.table
+    %thead
+      %tr
+        %th Commit
+        %th Tip (relative to the project balance)
+    %tbody
+      = f.fields_for(:tips, @project.tips.undecided) do |tip_fields|
+        = tip_fields.hidden_field :id
+        - tip = tip_fields.object
+        %tr
+          %td
+            = link_to tip.commit, tip.commit_url
+          %td
+            - radios = {}
+            - radios["Undecided"] = ""
+            - radios["Free: 0%"] = "0"
+            - radios["Tiny: 0.1%"] = "0.1"
+            - radios["Small: 0.5%"] = "0.5"
+            - radios["Normal: 1%"] = "1"
+            - radios["Big: 2%"] = "2"
+            - radios["Huge: 5%"] = "5"
+            = tip_fields.radio_buttons(:amount_percentage, radios, inline: true, label: false)
+  .text-center
+    = f.submit 'Send the selected tip amounts'
diff --git a/app/views/projects/show.html.haml b/app/views/projects/show.html.haml
index db634e0c..dd79d504 100644
--- a/app/views/projects/show.html.haml
+++ b/app/views/projects/show.html.haml
@@ -8,6 +8,8 @@
   = @project.full_name
   %small= link_to glyph(:github), @project.github_url, target: '_blank'
   = link_to "Change project settings", edit_project_path(@project), class: "btn btn-default"
+  - if @project.has_undecided_tips?
+    = link_to "Decide tip amounts", decide_tip_amounts_project_path(@project), class: "btn btn-primary"
 
 .row
   .col-md-4
diff --git a/app/views/tips/index.html.haml b/app/views/tips/index.html.haml
index dca6a51a..df75befd 100644
--- a/app/views/tips/index.html.haml
+++ b/app/views/tips/index.html.haml
@@ -32,6 +32,8 @@
             - if tip.sendmany.nil?
               - if tip.refunded_at
                 Refunded to project's deposit
+              - elsif tip.undecided?
+                The amount of tips has not been decided yet
               - elsif tip.user.bitcoin_address.blank?
                 User didn't specify withdrawal address
               - elsif tip.project.amount_to_pay < CONFIG["min_payout"].to_d * PeercoinBalanceUpdater::COIN
diff --git a/config/routes.rb b/config/routes.rb
index bb16e470..6ee4ad84 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -14,6 +14,8 @@
     resources :tips, :only => [:index]
     member do
       get :qrcode
+      get :decide_tip_amounts
+      patch :decide_tip_amounts
     end
   end
   resources :tips, :only => [:index]
diff --git a/features/step_definitions/common.rb b/features/step_definitions/common.rb
index a3a924b8..8e10884a 100644
--- a/features/step_definitions/common.rb
+++ b/features/step_definitions/common.rb
@@ -6,6 +6,10 @@
   ActionMailer::Base.deliveries.size.should eq(arg1.to_i)
 end
 
+When(/^the email counters are reset$/) do
+  ActionMailer::Base.deliveries.clear
+end
+
 Given(/^the tip for commit is "(.*?)"$/) do |arg1|
   CONFIG["tip"] = arg1.to_f
 end
@@ -67,11 +71,13 @@ def find_new_commit(id)
 end
 
 Then(/^there should be a tip of "(.*?)" for commit "(.*?)"$/) do |arg1, arg2|
-  (Tip.find_by(commit: arg2).amount.to_d / PeercoinBalanceUpdater::COIN).should eq(arg1.to_d)
+  amount = Tip.find_by(commit: arg2).amount
+  amount.should_not be_nil
+  (amount.to_d / PeercoinBalanceUpdater::COIN).should eq(arg1.to_d)
 end
 
 Then(/^the tip amount for commit "(.*?)" should be undecided$/) do |arg1|
-  Tip.find_by(commit: arg1).amount_undecided?.should be_true
+  Tip.find_by(commit: arg1).undecided?.should be_true
 end
 
 Then(/^the new last known commit should be "(.*?)"$/) do |arg1|
diff --git a/features/step_definitions/tip_modifier_interface.rb b/features/step_definitions/tip_modifier_interface.rb
index e69de29b..ad2bbb05 100644
--- a/features/step_definitions/tip_modifier_interface.rb
+++ b/features/step_definitions/tip_modifier_interface.rb
@@ -0,0 +1,5 @@
+When(/^I choose the amount "(.*?)" on commit "(.*?)"$/) do |arg1, arg2|
+  within find("tr", text: arg2) do
+    choose arg1
+  end
+end
diff --git a/features/step_definitions/web.rb b/features/step_definitions/web.rb
index c3ee3013..78fbe4a9 100644
--- a/features/step_definitions/web.rb
+++ b/features/step_definitions/web.rb
@@ -28,3 +28,7 @@
   page.should have_content(arg1)
 end
 
+Then(/^I should not see "(.*?)"$/) do |arg1|
+  page.should have_no_content(arg1)
+end
+
diff --git a/features/tip_modifier_interface.feature b/features/tip_modifier_interface.feature
index 4be55301..b250b2a0 100644
--- a/features/tip_modifier_interface.feature
+++ b/features/tip_modifier_interface.feature
@@ -6,13 +6,16 @@ Feature: A project collaborator can change the tips of commits
       | daneel  |
     And our fee is "0"
     And a deposit of "500"
-    And the last known commit is "A"
-    And a new commit "B" with parent "A"
-    And the author of commit "B" is "yugo"
+    And the last known commit is "AAA"
+    And a new commit "BBB" with parent "AAA"
+    And a new commit "CCC" with parent "BBB"
+    And the author of commit "BBB" is "yugo"
+    And the author of commit "CCC" is "seldon"
 
   Scenario: Without anything modified
     When the new commits are read
-    Then there should be a tip of "5" for commit "B"
+    Then there should be a tip of "5" for commit "BBB"
+    And there should be a tip of "4.95" for commit "CCC"
     And there should be 1 email sent
 
   Scenario: A collaborator wants to alter the tips
@@ -24,6 +27,26 @@ Feature: A project collaborator can change the tips of commits
     Then I should see "The project settings have been updated"
 
     When the new commits are read
-    Then the tip amount for commit "B" should be undecided
+    Then the tip amount for commit "BBB" should be undecided
+    And the tip amount for commit "CCC" should be undecided
+    And there should be 0 email sent
+
+    When I go to the project page
+    And I click on "Decide tip amounts"
+    Then I should see "BBB"
+    And I should see "CCC"
+    And I should not see "AAA"
+
+    When I choose the amount "Tiny: 0.1%" on commit "BBB"
+    And I click on "Send the selected tip amounts"
+    Then there should be a tip of "0.5" for commit "BBB"
+    And the tip amount for commit "CCC" should be undecided
+    And there should be 1 email sent
+
+    When the email counters are reset
+    And I choose the amount "Free: 0%" on commit "CCC"
+    And I click on "Send the selected tip amounts"
+    Then there should be a tip of "0.5" for commit "BBB"
+    And there should be a tip of "0" for commit "CCC"
     And there should be 0 email sent