diff --git a/pkgs/by-name/cg/cgtcalc/generated/default.nix b/pkgs/by-name/cg/cgtcalc/generated/default.nix
new file mode 100644
index 000000000000..fcda4cfc1a87
--- /dev/null
+++ b/pkgs/by-name/cg/cgtcalc/generated/default.nix
@@ -0,0 +1,7 @@
+# This file was generated by swiftpm2nix.
+{
+  workspaceStateFile = ./workspace-state.json;
+  hashes = {
+    "swift-argument-parser" = "sha256-lWQ9mzfRxHcy00Cqyrsm9rOlQzkpU1lNBmiK7MMp6dU=";
+  };
+}
diff --git a/pkgs/by-name/cg/cgtcalc/generated/workspace-state.json b/pkgs/by-name/cg/cgtcalc/generated/workspace-state.json
new file mode 100644
index 000000000000..3a9ec58c7166
--- /dev/null
+++ b/pkgs/by-name/cg/cgtcalc/generated/workspace-state.json
@@ -0,0 +1,25 @@
+{
+  "object": {
+    "artifacts": [],
+    "dependencies": [
+      {
+        "basedOn": null,
+        "packageRef": {
+          "identity": "swift-argument-parser",
+          "kind": "remoteSourceControl",
+          "location": "https://github.com/apple/swift-argument-parser",
+          "name": "swift-argument-parser"
+        },
+        "state": {
+          "checkoutState": {
+            "revision": "f3c9084a71ef4376f2fabbdf1d3d90a49f1fabdb",
+            "version": "1.1.2"
+          },
+          "name": "sourceControlCheckout"
+        },
+        "subpath": "swift-argument-parser"
+      }
+    ]
+  },
+  "version": 6
+}
diff --git a/pkgs/by-name/cg/cgtcalc/package.nix b/pkgs/by-name/cg/cgtcalc/package.nix
new file mode 100644
index 000000000000..eae6cbd7e32e
--- /dev/null
+++ b/pkgs/by-name/cg/cgtcalc/package.nix
@@ -0,0 +1,58 @@
+{
+  fetchFromGitHub,
+  lib,
+  nix-update-script,
+  stdenv,
+  swift,
+  swiftPackages,
+  swiftpm,
+  swiftpm2nix,
+}:
+let
+  generated = swiftpm2nix.helpers ./generated;
+in
+stdenv.mkDerivation (finalAttrs: {
+  pname = "cgtcalc";
+  version = "0-unstable-2025-10-11";
+
+  src = fetchFromGitHub {
+    owner = "mattjgalloway";
+    repo = "cgtcalc";
+    # Repo has no tags or releases.
+    # This is the last commit before requiring Swift 6
+    rev = "1cf63741ddc0a5070680cb1339ad0abff0b7d69b";
+    hash = "sha256-+qgvl5y9ipVQIZlLZbkzkqb9bO7X9VGDvVsloOLZU/k=";
+  };
+  nativeBuildInputs = [
+    swift
+    swiftpm
+  ];
+
+  configurePhase = generated.configure;
+
+  installPhase = ''
+    runHook preInstall
+    mkdir -p $out/bin
+    cp $(swiftpmBinPath)/cgtcalc $out/bin/
+    runHook postInstall
+  '';
+
+  buildInputs = [
+    swiftPackages.XCTest
+  ];
+
+  # libIndexStore.so: cannot open shared object file: No such file or directory
+  # https://github.com/NixOS/nixpkgs/issues/379859
+  doCheck = false;
+
+  passthru.updateScript = nix-update-script { };
+
+  meta = {
+    description = "UK capital gains tax calculator written in Swift";
+    homepage = "https://github.com/mattjgalloway/cgtcalc";
+    license = lib.licenses.mit;
+    maintainers = [ lib.maintainers.dwoffinden ];
+    mainProgram = "cgtcalc";
+    platforms = lib.platforms.all;
+  };
+})