diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6ab2890..b5bfd74 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,13 @@
+## [9.0.0] - 2026-03-20
+
+* Restore support for .NET Core version 9.0 (supported versions are now 9.0 and 10.0)
+
+## [8.0.0] - (unreleased)
+
+* Updates versions of JWT and Newtonsoft.JSON dependencies
+* Drops support for .NET Core version 9.0 or earlier
+* Drops support for .NET Framework
+
 ## [7.2.0] - 2024-07-31
 * Added fields related to cost data in response:
   * `is_cost_data_ready`: This field is true if cost data is ready, and false if it isn't (Boolean).
diff --git a/Makefile b/Makefile
index f2f2ace..4a701a6 100644
--- a/Makefile
+++ b/Makefile
@@ -6,7 +6,7 @@ help:
 
 .PHONY: build
 build: ## Build project
-	dotnet build -f=net10.0
+	dotnet build
 
 .PHONY: format
 format:
@@ -22,15 +22,15 @@ test: single-test
 
 .PHONY: single-test
 single-test: build ## run a single test. usage: "make single-test test=[test name]"
-	dotnet test ./src/GovukNotify.Tests/GovukNotify.Tests.csproj -f=net10.0 --no-build -v=n --filter $(test)
+	dotnet test ./src/GovukNotify.Tests/GovukNotify.Tests.csproj --no-build -v=n --filter $(test)
 
 .PHONY: build-release
 build-release: ## Build release version
-	dotnet build -c=Release -f=net10.0
+	dotnet build -c=Release
 
 .PHONY: build-package
 build-package: build-release ## Build and package NuGet
-	dotnet pack -c=Release ./src/GovukNotify/GovukNotify.csproj /p:TargetFrameworks=net8,net9,net10 -o=publish
+	dotnet pack -c=Release ./src/GovukNotify/GovukNotify.csproj -o=publish
 
 .PHONY: bootstrap-with-docker
 bootstrap-with-docker:  ## Prepare the Docker builder image
diff --git a/appveyor.txt b/appveyor.txt
index 7c3f911..fb19095 100644
--- a/appveyor.txt
+++ b/appveyor.txt
@@ -1,3 +1,7 @@
+install:
+- ps: |
+    Invoke-WebRequest -Uri 'https://dot.net/v1/dotnet-install.ps1' -UseBasicParsing -OutFile "$env:temp\dotnet-install.ps1"
+    & $env:temp\dotnet-install.ps1 -Architecture x64 -Version '10.0.100' -InstallDir "$env:ProgramFiles\dotnet"
 clone_script:
 - cmd: >-
     git clone -q --branch=main https://github.com/alphagov/notifications-net-client.git C:\projects\notifications-net-client
@@ -31,6 +35,8 @@ environment:
   pullId: 0
 build: off
 image: Visual Studio 2022
+before_test:
+  - cmd: dotnet --version
 test_script: dotnet test C:\projects\notifications-net-client\src\GovukNotify.Tests -c=Release
 on_success:
 - publish.cmd
diff --git a/src/GovukNotify.Tests/GovukNotify.Tests.csproj b/src/GovukNotify.Tests/GovukNotify.Tests.csproj
index 7b37925..c8e188b 100644
--- a/src/GovukNotify.Tests/GovukNotify.Tests.csproj
+++ b/src/GovukNotify.Tests/GovukNotify.Tests.csproj
@@ -1,8 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net10.0</TargetFrameworks>
-
+    <TargetFrameworks>net10.0;net9.0</TargetFrameworks>
+    <LangVersion>14.0</LangVersion>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
diff --git a/src/GovukNotify/GovukNotify.csproj b/src/GovukNotify/GovukNotify.csproj
index 35bf967..2827993 100644
--- a/src/GovukNotify/GovukNotify.csproj
+++ b/src/GovukNotify/GovukNotify.csproj
@@ -2,8 +2,8 @@
 
   <PropertyGroup>
     <RestoreProjectStyle>PackageReference</RestoreProjectStyle>
-    <TargetFrameworks>net10.0</TargetFrameworks>
-    <Version>8.0.0</Version>
+    <TargetFrameworks>net10.0;net9.0</TargetFrameworks>
+    <Version>9.0.0</Version>
     <Authors>GOV.UK Notify</Authors>
     <Description>GOV.UK .NET Notify Client</Description>
     <PackageRequireLicenseAcceptance>false</PackageRequireLicenseAcceptance>
@@ -20,8 +20,4 @@
     <PackageReference Include="Newtonsoft.Json" Version="[13.0.4,14]" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net462' ">
-    <PackageReference Include="System.Net.Http" Version="4.3.4" />
-  </ItemGroup>
-
 </Project>