diff --git a/.rubocop.yml b/.rubocop.yml
index adfe750..9059597 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -452,3 +452,6 @@ Style/SymbolProc:
 
 Style/ZeroLengthPredicate:
   Enabled: false
+
+Style/MutableConstant:
+  Enabled: false
diff --git a/Gemfile.lock b/Gemfile.lock
index 1e675d5..6c6f6af 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -3,6 +3,7 @@ PATH
   specs:
     xpm_ruby (0.1.0)
       faraday (~> 1)
+      nokogiri
       ox (~> 2.13)
 
 GEM
@@ -16,7 +17,10 @@ GEM
       multipart-post (>= 1.2, < 3)
     jaro_winkler (1.5.4)
     method_source (1.0.0)
+    mini_portile2 (2.4.0)
     multipart-post (2.1.1)
+    nokogiri (1.10.9)
+      mini_portile2 (~> 2.4.0)
     ox (2.13.2)
     parallel (1.19.1)
     parser (2.7.1.1)
diff --git a/lib/xpm_ruby.rb b/lib/xpm_ruby.rb
index c00a877..5f347b2 100644
--- a/lib/xpm_ruby.rb
+++ b/lib/xpm_ruby.rb
@@ -3,8 +3,12 @@ class Error < StandardError; end
   class Unauthorized < Error; end
 end
 
+require "nokogiri"
+
+require "xpm_ruby/version"
 require "xpm_ruby/connection"
 require "xpm_ruby/job"
 require "xpm_ruby/staff"
+require "xpm_ruby/client"
 require "xpm_ruby/template"
 require "xpm_ruby/version"
diff --git a/lib/xpm_ruby/client.rb b/lib/xpm_ruby/client.rb
new file mode 100644
index 0000000..9e31bbc
--- /dev/null
+++ b/lib/xpm_ruby/client.rb
@@ -0,0 +1,49 @@
+require "faraday"
+require "base64"
+require "ox"
+
+require_relative "client/get"
+require_relative "client/add"
+
+module XpmRuby
+  module Client
+    extend self
+
+    module GstPeriod
+      ONE = "1"
+      TWO = "2"
+      SIX = "6"
+    end
+
+    module GstBasis
+      INVOICE = "Invoice"
+      PAYMENT = "Payment"
+      HYBRID = "Hybrid"
+    end
+
+    module ProvisionalTaxBasis
+      STANDARD_OPTION = "Standard Option"
+      ESTIMATE_OPTION = "Estimate Option"
+      RATIO_OPTION = "Ratio Option"
+    end
+
+    module AgencyStatus
+      WITH_EOT = "With EOT"
+      WITHOUT_EOT = "Without EOT"
+      UNLINKED = "Unlinked"
+    end
+
+    module ReturnType
+      IR3 = "IR3"
+      IR3NR = "IR3NR"
+      IR4 = "IR4"
+      IR6 = "IR6"
+      IR7 = "IR7"
+      IR9 = "IR9"
+      PTS = "PTS"
+    end
+
+    class Error < StandardError; end
+    class Unauthorized < Error; end
+  end
+end
diff --git a/lib/xpm_ruby/client/add.rb b/lib/xpm_ruby/client/add.rb
new file mode 100644
index 0000000..16c9cfc
--- /dev/null
+++ b/lib/xpm_ruby/client/add.rb
@@ -0,0 +1,245 @@
+# client.api/add
+#
+# <Client>
+#   <Name>Bloggs Electrical Ltd</Name>
+#   <Email></Email>  <!-- optional -->
+#   <Address></Address>  <!-- optional -->
+#   <City></City>  <!-- optional -->
+#   <Region></Region>  <!-- optional -->
+#   <PostCode></PostCode>  <!-- optional -->
+#   <Country></Country>  <!-- optional -->
+#   <PostalAddress></PostalAddress>  <!-- optional -->
+#   <PostalCity></PostalCity>  <!-- optional -->
+#   <PostalRegion></PostalRegion>  <!-- optional -->
+#   <PostalPostCode></PostalPostCode>  <!-- optional -->
+#   <PostalCountry></PostalCountry>  <!-- optional -->
+#   <Phone></Phone>  <!-- optional -->
+#   <Fax></Fax>  <!-- optional -->
+#   <WebSite></WebSite>  <!-- optional -->
+#   <ReferralSource></ReferralSource>  <!-- optional -->
+#   <ExportCode></ExportCode>  <!-- optional -->
+#   <IsProspect>No</IsProspect>    <!-- Yes | No -->
+#   <AccountManagerUUID />  <!-- optional - UUID of staff member -->
+#   <Contacts>
+#     <Contact>
+#       <Name>Jo Bloggs</Name>
+#       <IsPrimary>yes</IsPrimary> <!-- If multiple contacts defined, method will interpret last primary client as Primary -->
+#       <Salutation></Salutation>  <!-- optional -->
+#       <Addressee></Addressee>  <!-- optional -->
+#       <Phone></Phone>  <!-- optional -->
+#       <Mobile></Mobile>  <!-- optional -->
+#       <Email></Email>  <!-- optional -->
+#       <Position></Position>  <!-- optional -->
+#     </Contact>
+#   </Contacts>
+#   <BillingClientUUID /> <!-- optional UUID of billing client -->
+
+#   <!-- The following fields are only applicable if the Practice Management module is enabled -->
+
+#   <FirstName />   <!-- optional, for individuals only -->
+#   <LastName />   <!-- optional, for individuals only -->
+#   <OtherName />   <!-- optional, for individuals only -->
+#   <DateOfBirth />   <!-- optional, for individuals only -->
+
+#   <JobManagerUUID />  <!-- optional - UUID of staff member -->
+#   <TaxNumber />
+#   <CompanyNumber />
+#   <BusinessNumber />
+#   <BusinessStructure />   <!-- Name of Business Structure (as per Admin) -->
+#   <BalanceMonth />  <!-- e.g. Jan, 1, Feb, 2, Mar, 3 etc  -->
+#   <PrepareGST />   <!-- Yes or No -->
+#   <GSTRegistered />   <!-- Yes or No -->
+#   <GSTPeriod />  <!-- 1, 2, 6 -->
+#   <GSTBasis />  <!-- Invoice, Payment, Hybrid  -->
+#   <ProvisionalTaxBasis />  <!-- Standard Option, Estimate Option, Ratio Option  -->
+#   <ProvisionalTaxRatio />
+
+#   <!-- The following fields apply to NZ clients only -->
+#   <SignedTaxAuthority />  <!-- Yes or No -->
+#   <TaxAgent />  <!-- Name of Tax Agent (as per Admin) -->
+#   <AgencyStatus />  <!-- With EOT, Without EOT, Unlinked -->
+#   <ReturnType />  <!-- IR3, IR3NR, IR4, IR6, IR7, IR9, PTS  -->
+
+#   <!-- The following fields apply to AU clients only -->
+#   <PrepareActivityStatement />  <!-- Yes or No -->
+#   <PrepareTaxReturn />  <!-- Yes or No -->
+# </Client>
+
+module XpmRuby
+  module Client
+    module Add
+      extend self
+
+      def call(api_key:, account_key:, api_url:, client:)
+        builder = ::Nokogiri::XML::Builder.new do |xml|
+          xml.Client do
+            xml.Name do
+              xml.text(client.name)
+            end
+          end
+        end
+
+        response = Connection
+          .new(api_key: api_key, account_key: account_key, api_url: api_url)
+          .post(endpoint: "client.api/add", data: builder.doc.root.to_xml)
+
+        case response.status
+        when 401
+          hash = Ox.load(response.body, mode: :hash_no_attrs, symbolize_keys: false)
+
+          raise Unauthorized.new(hash["html"]["head"]["title"])
+        when 200
+          hash = Ox.load(response.body, mode: :hash_no_attrs, symbolize_keys: false)
+
+          case hash["Response"]["Status"]
+          when "OK"
+            Get::Client.new(
+              uuid: hash["Response"]["Client"]["UUID"],
+              name: hash["Response"]["Client"]["Name"],
+              email: hash["Response"]["Client"]["Email"])
+          when "ERROR"
+            raise Error.new(response["ErrorDescription"])
+          end
+        else
+          raise Error.new(response.status)
+        end
+      end
+
+      class Client
+        attr_accessor :name, :email, :address, :city, :region, :post_code, :country,
+          :postal_address, :postal_city, :postal_region, :postal_post_code, :postal_country,
+          :phone, :fax, :web_site, :referral_source, :export_code, :is_prospect,
+          :account_manager_uuid, :contacts, :billing_client_uuid,
+          :first_name, :last_name, :other_name, :date_of_birth, :job_manager_uuid,
+          :tax_number, :company_number, :business_number, :business_structure, :balance_month,
+          :prepare_gst, :gst_registered, :gst_period, :gst_basis,
+          :provisional_tax_basis, :provisional_tax_ratio,
+          :signed_tax_authority, :tax_agent, :agency_status, :return_type,
+          :prepare_activity_statement, :prepare_tax_return
+
+        # rubocop:disable Metrics/AbcSize
+        def initialize(name:, email: nil,
+                      address: nil, city: nil, region: nil, post_code: nil, country: nil,
+                      postal_address: nil, postal_city: nil, postal_region: nil,
+                      postal_post_code: nil, postal_country: nil,
+                      phone: nil, fax: nil, web_site: nil,
+                      referral_source: nil, export_code: nil, is_prospect: nil,
+                      account_manager_uuid: nil, contacts: nil, billing_client_uuid: nil,
+                      first_name: nil, last_name: nil, other_name: nil, date_of_birth: nil,
+                      job_manager_uuid: nil, tax_number: nil, company_number: nil,
+                      business_number: nil, business_structure: nil, balance_month: nil,
+                      prepare_gst: nil, gst_registered: nil, gst_period: nil, gst_basis: nil,
+                      provisional_tax_basis: nil, provisional_tax_ratio: nil,
+                      signed_tax_authority: nil, tax_agent: nil, agency_status: nil,
+                      return_type: nil, prepare_activity_statement: nil, prepare_tax_return: nil)
+          @name =  name
+          @email = email
+          @address = address
+          @city = city
+          @region = region
+          @post_code = post_code
+          @country = country
+          @postal_address = postal_address
+          @postal_city = postal_city
+          @postal_region = postal_region
+          @postal_post_code = postal_post_code
+          @postal_country = postal_country
+          @phone = phone
+          @fax = fax
+          @web_site = web_site
+          @referral_source = referral_source
+          @export_code = export_code
+          @is_prospect = is_prospect
+          @account_manager_uuid = account_manager_uuid
+          @contacts = contacts
+          @billing_client_uuid = billing_client_uuid
+          @first_name = first_name
+          @last_name = last_name
+          @other_name = other_name
+          @date_of_birth = date_of_birth
+          @job_manager_uuid = job_manager_uuid
+          @tax_number = tax_number
+          @company_number = company_number
+          @business_number = business_number
+          @business_structure = business_structure
+          @balance_month = balance_month
+          @prepare_gst = prepare_gst
+          @gst_registered = gst_registered
+          @gst_period = gst_period
+          @gst_basis = gst_basis
+          @provisional_tax_basis = provisional_tax_basis
+          @provisional_tax_rate = provisional_tax_ratio
+          @signed_tax_authority = signed_tax_authority
+          @tax_agent = tax_agent
+          @agency_status = agency_status
+          @return_type = return_type
+          @prepare_activity_statement = prepare_activity_statement
+          @prepare_tax_return = prepare_tax_return
+        end
+        # rubocop:enable Metrics/AbcSize
+
+        class AccountManager
+          attr_reader :uuid, :name
+
+          def initialize(uuid: nil, name: nil)
+            @uuid = uuid
+            @name = name
+          end
+
+          def ==(other)
+            uuid == other.uuid
+          end
+
+          def eql?(other)
+            self == other
+          end
+        end
+
+        class Type
+          attr_reader :name, :cost_markup, :payment_term, :payment_day
+
+          def initialize(name: nil, cost_markup: nil, payment_term: nil, payment_day: nil)
+            @name = name
+            @cost_markup = cost_markup
+            @payment_term = payment_term
+            @payment_day = payment_day
+          end
+
+          def ==(other)
+            name == other.name &&
+            cost_markup == other.cost_markup &&
+            payment_term == other.payment_term &&
+            payment_day == other.payment_day
+          end
+
+          def eql?(other)
+            self == other
+          end
+        end
+
+        class Contact
+          def initialize(uuid: nil, is_primary: nil, name: nil, salutation: nil,
+                        addressee: nil, mobile: nil, email: nil, phone: nil, position: nil)
+            @uuid = uuid
+            @is_primary = is_primary
+            @name = name
+            @salutation = salutation
+            @addressee = addressee
+            @mobile = mobile
+            @email = email
+            @phone = phone
+            @position = position
+          end
+
+          def ==(other)
+            uuid == other.uuid
+          end
+
+          def eql?(other)
+            self == other
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/xpm_ruby/client/get.rb b/lib/xpm_ruby/client/get.rb
new file mode 100644
index 0000000..18ca2c0
--- /dev/null
+++ b/lib/xpm_ruby/client/get.rb
@@ -0,0 +1,134 @@
+# client.api/get
+
+# <Response>
+#   <Status>OK</Status>
+#   <Client>
+#   <UUID>c257b062-fbc9-4dc7-9132-f18ee956c4f9</UUID>
+#   <Name>Acmer Pty Ltd</Name>
+#   <Email>someone@example.com</Email>
+#   <DateOfBirth>1970-11-26</DateOfBirth>
+#   <Address />
+#   <City />
+#   <Region />
+#   <PostCode />
+#   <Country />
+#   <PostalAddress>
+#   Level 32, PWC Building
+#   188 Quay Street
+#   Auckland Central
+#   </PostalAddress>
+#   <PostalCity>Auckland</PostalCity>
+#   <PostalRegion />
+#   <PostalPostCode>1001</PostalPostCode>
+#   <PostalCountry />
+#   <Phone>(02) 1723 5265</Phone>
+#   <Fax />
+#   <Website />
+#   <ReferralSource />
+#   <ExportCode />
+#   <IsProspect>No</IsProspect>
+#   <AccountManager>
+#     <UUID>ab3d6db0-f0be-4a3e-bd68-8fad1c6b40bb</UUID>
+#     <Name>Jo Blogs</Name>
+#   </AccountManager>
+#   <Type>
+#     <Name>20th of Month</Name>
+#     <CostMarkup>30.00</CostMarkup>
+#     <PaymentTerm>DayOfMonth</PaymentTerm> <!-- DayOfMonth or WithinDays -->
+#     <PaymentDay>20</PaymentDay>
+#   </Type>
+#   <Contacts>
+#   <Contact>
+#   <UUID>f1ec264f-d269-4232-9615-c167583fa7da</UUID>
+#   <IsPrimary>yes</IsPrimary>
+#   <Name>Wyett E Coyote</Name>
+#   <Salutation />
+#   <Addressee />
+#   <Mobile />
+#   <Email />
+#   <Phone />
+#   <Position />
+#   </Contact>
+#   </Contacts>
+#   <Notes>
+#     <Note>
+#       <Title>note title</Title>
+#       <Text>subject of the note</Text>
+#       <Folder />
+#       <Date>2008-09-12T13:00:00</Date>
+#       <CreatedBy>Jo Bloggs</CreatedBy>
+#     </Note>
+#   </Notes>
+#   <BillingClient>
+#     <UUID>e41ecd7a-ac85-4473-a7b3-052bd670f01e</UUID>
+#     <Name>Billing Client</Name>
+#   </BillingClient>
+#   <!-- The following fields are returned if the Practice Management module is enabled -->
+#   <JobManager>
+#     <UUID>ebc0e2ae-3d3e-4546-9787-8c659e445d31</UUID>
+#     <Name>John Smith</Name>
+#   </JobManager>
+#   <FirstName /> <!-- Individual Only -->
+#   <LastName /> <!-- Individual Only -->
+#   <OtherName /> <!-- Individual Only -->
+#   <DateOfBirth /> <!-- Individual Only -->
+#   <TaxNumber /> ******123 <!-- e.g. where the tax number is masked with *** except last 3 digits -->
+#   <CompanyNumber />
+#   <BusinessNumber />
+#   <BusinessStructure /> <!-- e.g. Individual, Company, Trust, etc -->
+#   <BalanceMonth />
+#   <PrepareGST /> <!-- Yes or No -->
+#   <GSTRegistered /> <!-- Yes or No -->
+#   <GSTPeriod /> <!-- Monthly, 2 Monthly, 6 Monthly -->
+#   <GSTBasis /> <!-- Invoice, Payment, Hybrid -->
+#   <ProvisionalTaxBasis /> <!-- Standard Option, Estimate Option, Ratio Option -->
+#   <ProvisionalTaxRatio />
+#   <!-- The following fields apply to NZ clients only -->
+#   <SignedTaxAuthority /> <!-- Yes or No -->
+#   <TaxAgent />
+#   <AgencyStatus /> <!-- With EOT, Without EOT, Unlinked -->
+#   <ReturnType /> <!-- IR3, IR3NR, IR4, IR6, IR7, IR9, PTS -->
+#   <!-- The following fields apply to AU clients only -->
+#   <PrepareActivityStatement /> <!-- Yes or No -->
+#   <PrepareTaxReturn /> <!-- Yes or No -->
+#   <Groups>
+#     <Group>
+#       <UUID>9c3abe09-6df2-4f18-8090-36a44e91a1c3</UUID>
+#       <Name>Bloggs Family</Name>
+#     </Group>
+#   </Groups>
+#   <Relationships>
+#     <Relationship>
+#       <UUID>9c3abe09-6df2-4f18-8090-36a44e91a1c3</UUID>
+#       <Type>Shareholder</Type>
+#       <RelatedClient>
+#       <UUID>651ec79a-93cb-458c-b5ca-e123c92192b6</UUID>
+#       <Name>Bloggs Ltd</Name>
+#       </RelatedClient>
+#       <NumberOfShares>1000</NumberOfShares> <!-- Only set for Shareholder and Owner relationships --
+#       >
+#       <Percentage>0</Percentage> <!-- Only set for Partnership relationships-->
+#       <StartDate>2011-01-01</StartDate>
+#       <EndDate>2013-03-31</EndDate>
+#     </Relationship>
+#   </Relationships>
+#   </Client>
+# </Response>
+
+module XpmRuby
+  module Client
+    module Get
+      extend self
+
+      class Client
+        attr_accessor :uuid, :name, :email
+
+        def initialize(uuid:, name:, email: nil)
+          @uuid = uuid
+          @name = name
+          @email = email
+        end
+      end
+    end
+  end
+end
diff --git a/spec/vcr_cassettes/xpm_ruby/client/add.yml b/spec/vcr_cassettes/xpm_ruby/client/add.yml
new file mode 100644
index 0000000..94cbdbe
--- /dev/null
+++ b/spec/vcr_cassettes/xpm_ruby/client/add.yml
@@ -0,0 +1,51 @@
+---
+http_interactions:
+- request:
+    method: post
+    uri: https://api.workflowmax.com/v3/client.api/add
+    body:
+      encoding: UTF-8
+      string: |-
+        <Client>
+          <Name>Acmer Pty Ltd</Name>
+        </Client>
+    headers:
+      User-Agent:
+      - Faraday v1.0.1
+      Authorization:
+      - Basic
+      Content-Type:
+      - application/x-www-form-urlencoded
+  response:
+    status:
+      code: 200
+      message: OK
+    headers:
+      access-control-allow-origin:
+      - "*"
+      cache-control:
+      - private
+      content-type:
+      - text/xml; charset=utf-8
+      date:
+      - Tue, 28 Apr 2020 01:52:47 GMT
+      server:
+      - Microsoft-IIS/10.0
+      vary:
+      - Accept-Encoding
+      x-aspnet-version:
+      - 4.0.30319
+      x-aspnetmvc-version:
+      - '4.0'
+      content-length:
+      - '449'
+      connection:
+      - keep-alive
+    body:
+      encoding: ASCII-8BIT
+      string: <Response api-method="Add"><Status>OK</Status><Client><UUID>9f868ba7-437c-4574-9a17-8c6f4890545b</UUID><Name>Acmer
+        Pty Ltd</Name><Address></Address><City></City><Region></Region><PostCode></PostCode><Country></Country><PostalAddress></PostalAddress><PostalCity></PostalCity><PostalRegion></PostalRegion><PostalPostCode></PostalPostCode><PostalCountry></PostalCountry><Phone></Phone><Fax></Fax><Website></Website><ReferralSource></ReferralSource><ExportCode></ExportCode><IsProspect>No</IsProspect><IsArchived>No</IsArchived><IsDeleted>No</IsDeleted><Contacts
+        /><Notes /><Groups /><Relationships /></Client></Response>
+    http_version: null
+  recorded_at: Tue, 28 Apr 2020 01:52:48 GMT
+recorded_with: VCR 5.1.0
diff --git a/spec/xpm_ruby/client/add_spec.rb b/spec/xpm_ruby/client/add_spec.rb
new file mode 100644
index 0000000..903d579
--- /dev/null
+++ b/spec/xpm_ruby/client/add_spec.rb
@@ -0,0 +1,85 @@
+require "spec_helper"
+
+module XpmRuby
+  module Client
+    RSpec.describe(Add) do
+      around(:each) do |example|
+        VCR.use_cassette("xpm_ruby/client/add") do
+          example.run
+        end
+      end
+
+      describe ".call" do
+        let(:api_key) { "" }
+        let(:account_key) { "" }
+        let(:api_url) { "api.workflowmax.com" }
+
+        let(:client) do
+          Client::Add::Client.new(
+            name: "Acmer Pty Ltd",
+            email: "someone@example.com",
+            address: "1 Address Place",
+            city: "Sydney",
+            region: "NSW",
+            post_code: "2000",
+            country: "Australia",
+            postal_address: "Level 32, PWC Building\n188 Quay Street\nAuckland Central",
+            postal_city: "Auckland",
+            postal_region: "North Island",
+            postal_post_code: "1001",
+            postal_country: "New Zealand",
+            phone: "00 0000 0000",
+            fax: "00 1000 0000",
+            web_site: "http://example.com",
+            referral_source: "referrer",
+            export_code: "EXPORT_CODE",
+            is_prospect: false,
+            account_manager_uuid: nil,
+            contacts: [
+              Client::Add::Client::Contact.new(
+                name: "Someone else",
+                is_primary: true,
+                salutation: "MR",
+                addressee: "Addressee",
+                phone: "02 0000 0000",
+                mobile: "0411 0000 0000",
+                email: "someone.else@example.com",
+                position: "Manager")],
+            billing_client_uuid: nil,
+            first_name: "Someone",
+            last_name: "Person",
+            date_of_birth: Date.parse("1987/05/11"),
+            job_manager_uuid: nil,
+            tax_number: "11 1111 1111",
+            company_number: "02 1000 1000",
+            business_number: "02 1000 2000",
+            business_structure: "Corporate",
+            balance_month: "Jan",
+            prepare_gst: false,
+            gst_registered: true,
+            gst_period: Client::GstPeriod::ONE,
+            gst_basis: Client::GstBasis::INVOICE,
+            provisional_tax_basis: Client::ProvisionalTaxBasis::STANDARD_OPTION,
+            provisional_tax_ratio: "1",
+            signed_tax_authority: true,
+            tax_agent: "Mr Tax Agent",
+            agency_status: Client::AgencyStatus::WITH_EOT,
+            return_type: Client::ReturnType::IR3,
+            prepare_activity_statement: true,
+            prepare_tax_return: true)
+        end
+
+        it "adds client" do
+          created_client = Client::Add.call(
+            api_key: api_key,
+            account_key: account_key,
+            api_url: api_url,
+            client: client)
+
+          expect(created_client.uuid).not_to be_nil
+          expect(created_client.name).to eql(client.name)
+        end
+      end
+    end
+  end
+end
diff --git a/xpm_ruby.gemspec b/xpm_ruby.gemspec
index a8ea1c9..0ccf0e9 100644
--- a/xpm_ruby.gemspec
+++ b/xpm_ruby.gemspec
@@ -35,6 +35,8 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency("byebug", "~> 11")
   spec.add_development_dependency("pry-byebug", "~> 3")
 
+  spec.add_runtime_dependency("nokogiri")
+
   spec.add_runtime_dependency("faraday", "~> 1")
   spec.add_runtime_dependency("ox", "~> 2.13")