diff --git a/SongTidy.Tests/PlanXmlIOTests.cs b/SongTidy.Tests/PlanXmlIOTests.cs
new file mode 100644
index 0000000..68240fb
--- /dev/null
+++ b/SongTidy.Tests/PlanXmlIOTests.cs
@@ -0,0 +1,311 @@
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Xml.Linq;
+
+using SongTidy.Models;
+using SongTidy.Services;
+
+namespace SongTidy.Tests;
+
+/// <summary>
+/// Contains tests for <see cref="PlanXmlIO"/>.
+/// </summary>
+[TestClass]
+public sealed class PlanXmlIOTests {
+    #region Document structure
+
+    /// <summary>
+    /// Verifies the generated XML root, version, format, and item attributes.
+    /// </summary>
+    [TestMethod]
+    public void SavesExpectedDocumentStructure() {
+        SongPlan plan = CreateSamplePlan();
+
+        string xml = SaveToString(plan);
+        XDocument document = XDocument.Parse(xml);
+        XElement root = document.Root!;
+
+        Assert.AreEqual("Plan", root.Name.LocalName);
+        Assert.AreEqual(SongPlan.CurrentVersion.ToString(CultureInfo.InvariantCulture), root.Attribute("version")?.Value);
+        Assert.HasCount(1, root.Attributes());
+        Assert.AreEqual("ArtistFirst", root.Element("Format")?.Value);
+
+        XElement items = root.Element("Items")!;
+        Assert.HasCount(2, items.Elements("Item"));
+
+        XElement first = items.Elements("Item").First();
+        Assert.AreEqual(@"D:\Music\A - B (Live).mp3", first.Attribute("Path")?.Value);
+        Assert.AreEqual("A", first.Attribute("Artist")?.Value);
+        Assert.AreEqual("B", first.Attribute("Title")?.Value);
+        Assert.AreEqual("Live", first.Attribute("Comment")?.Value);
+
+        Assert.IsTrue(
+            xml.StartsWith("<?xml version=\"1.0\" encoding=\"utf-8\"?>", StringComparison.Ordinal),
+            "The XML declaration should specify UTF-8.");
+    }
+
+    /// <summary>
+    /// Verifies that empty fields are still written as empty attributes.
+    /// </summary>
+    [TestMethod]
+    public void WritesEmptyFieldsAsAttributes() {
+        SongPlan plan = new() {
+            Items = new List<PlanItem> {
+                new PlanItem {
+                    Path = @"C:\Music\C.mp3",
+                    Title = "C",
+                },
+            },
+        };
+
+        string xml = SaveToString(plan);
+        XElement item = XDocument.Parse(xml).Root!.Element("Items")!.Element("Item")!;
+
+        Assert.IsNotNull(item.Attribute("Artist"));
+        Assert.AreEqual(string.Empty, item.Attribute("Artist")!.Value);
+        Assert.IsNotNull(item.Attribute("Comment"));
+        Assert.AreEqual(string.Empty, item.Attribute("Comment")!.Value);
+    }
+
+    #endregion
+
+    #region Round trips
+
+    /// <summary>
+    /// Verifies that both format enum values survive a round trip.
+    /// </summary>
+    /// <param name="format">The format to round-trip.</param>
+    [TestMethod]
+    [DataRow(RenameFormat.ArtistFirst)]
+    [DataRow(RenameFormat.TitleFirst)]
+    public void RoundTripsFormat(RenameFormat format) {
+        SongPlan plan = new() {
+            Format = format,
+            Items = new List<PlanItem> {
+                new PlanItem { Path = @"C:\Music\C.mp3", Title = "C" },
+            },
+        };
+
+        SongPlan loaded = RoundTrip(plan);
+
+        Assert.AreEqual(format, loaded.Format);
+    }
+
+    /// <summary>
+    /// Verifies that every field and the version survive a round trip.
+    /// </summary>
+    [TestMethod]
+    public void RoundTripsAllFields() {
+        SongPlan plan = CreateSamplePlan();
+
+        SongPlan loaded = RoundTrip(plan);
+
+        Assert.AreEqual(plan.Version, loaded.Version);
+        Assert.AreEqual(plan.Format, loaded.Format);
+        Assert.HasCount(2, loaded.Items);
+        AssertPlanItem(plan.Items[0], loaded.Items[0]);
+        AssertPlanItem(plan.Items[1], loaded.Items[1]);
+    }
+
+    /// <summary>
+    /// Verifies that a non-default version attribute is preserved.
+    /// </summary>
+    [TestMethod]
+    public void PreservesVersion() {
+        SongPlan plan = CreateSamplePlan();
+        int version = SongPlan.CurrentVersion + 1;
+        plan.Version = version;
+
+        SongPlan loaded = RoundTrip(plan);
+
+        Assert.AreEqual(version, loaded.Version);
+    }
+
+    /// <summary>
+    /// Verifies that paths and fields containing spaces and XML special characters round-trip.
+    /// </summary>
+    [TestMethod]
+    public void RoundTripsPathsWithSpacesAndSpecialCharacters() {
+        const string path = @"D:\Music\A & B ""quoted"" <tag> 'single' - (Live).mp3";
+        SongPlan plan = new() {
+            Items = new List<PlanItem> {
+                new PlanItem {
+                    Path = path,
+                    Artist = "A & B",
+                    Title = "Title <tag>",
+                    Comment = "\"Comment\"",
+                },
+            },
+        };
+
+        string xml = SaveToString(plan);
+
+        Assert.IsTrue(xml.Contains("&amp;", StringComparison.Ordinal));
+        Assert.IsTrue(xml.Contains("&quot;", StringComparison.Ordinal));
+        Assert.IsTrue(xml.Contains("&lt;", StringComparison.Ordinal));
+        Assert.IsTrue(xml.Contains("&gt;", StringComparison.Ordinal));
+
+        SongPlan loaded = RoundTrip(plan);
+
+        Assert.AreEqual(path, loaded.Items[0].Path);
+        Assert.AreEqual("A & B", loaded.Items[0].Artist);
+        Assert.AreEqual("Title <tag>", loaded.Items[0].Title);
+        Assert.AreEqual("\"Comment\"", loaded.Items[0].Comment);
+    }
+
+    #endregion
+
+    #region Loading
+
+    /// <summary>
+    /// Verifies that missing optional attributes are loaded as empty strings.
+    /// </summary>
+    [TestMethod]
+    public void LoadsMissingOptionalAttributesAsEmpty() {
+        string xml = $"""
+            <?xml version="1.0" encoding="utf-8"?>
+            <Plan version="{SongPlan.CurrentVersion}">
+              <Format>TitleFirst</Format>
+              <Items>
+                <Item Path="C:\Music\C.mp3" Title="C" />
+              </Items>
+            </Plan>
+            """;
+
+        SongPlan plan = LoadFromString(xml);
+
+        Assert.AreEqual(RenameFormat.TitleFirst, plan.Format);
+        Assert.HasCount(1, plan.Items);
+        Assert.AreEqual(@"C:\Music\C.mp3", plan.Items[0].Path);
+        Assert.AreEqual(string.Empty, plan.Items[0].Artist);
+        Assert.AreEqual("C", plan.Items[0].Title);
+        Assert.AreEqual(string.Empty, plan.Items[0].Comment);
+    }
+
+    /// <summary>
+    /// Verifies that a missing Items element leaves an empty initialized list.
+    /// </summary>
+    [TestMethod]
+    public void LoadsMissingItemsAsEmptyList() {
+        string xml = $"""
+            <?xml version="1.0" encoding="utf-8"?>
+            <Plan version="{SongPlan.CurrentVersion}">
+              <Format>ArtistFirst</Format>
+            </Plan>
+            """;
+
+        SongPlan plan = LoadFromString(xml);
+
+        Assert.HasCount(0, plan.Items);
+    }
+
+    #endregion
+
+    #region File access
+
+    /// <summary>
+    /// Verifies file save and load with spaces in the file path and UTF-8 output without a BOM.
+    /// </summary>
+    [TestMethod]
+    public void SavesAndLoadsFileWithSpacesInPath() {
+        string directory = Path.Combine(Path.GetTempPath(), $"SongTidy Plan Test {Guid.NewGuid():N}");
+        string filePath = Path.Combine(directory, "plan with spaces.xml");
+        Directory.CreateDirectory(directory);
+
+        try {
+            SongPlan plan = CreateSamplePlan();
+
+            PlanXmlIO.Save(plan, filePath);
+
+            Assert.IsTrue(File.Exists(filePath));
+
+            byte[] bytes = File.ReadAllBytes(filePath);
+            Assert.AreEqual((byte)'<', bytes[0]);
+
+            string xml = Encoding.UTF8.GetString(bytes);
+            Assert.IsTrue(
+                xml.StartsWith("<?xml version=\"1.0\" encoding=\"utf-8\"?>", StringComparison.Ordinal),
+                "The file should be written as UTF-8 without a BOM.");
+
+            SongPlan loaded = PlanXmlIO.Load(filePath);
+            Assert.AreEqual(plan.Format, loaded.Format);
+            Assert.HasCount(plan.Items.Count, loaded.Items);
+            AssertPlanItem(plan.Items[0], loaded.Items[0]);
+        } finally {
+            Directory.Delete(directory, recursive: true);
+        }
+    }
+
+    #endregion
+
+    /// <summary>
+    /// Creates a sample plan containing two entries.
+    /// </summary>
+    /// <returns>The sample plan.</returns>
+    private static SongPlan CreateSamplePlan() {
+        return new SongPlan {
+            Format = RenameFormat.ArtistFirst,
+            Items = new List<PlanItem> {
+                new PlanItem {
+                    Path = @"D:\Music\A - B (Live).mp3",
+                    Artist = "A",
+                    Title = "B",
+                    Comment = "Live",
+                },
+                new PlanItem {
+                    Path = @"D:\Music\C.mp3",
+                    Artist = string.Empty,
+                    Title = "C",
+                    Comment = string.Empty,
+                },
+            },
+        };
+    }
+
+    /// <summary>
+    /// Saves a plan to an in-memory stream and returns the decoded XML.
+    /// </summary>
+    /// <param name="plan">The plan to save.</param>
+    /// <returns>The generated XML text.</returns>
+    private static string SaveToString(SongPlan plan) {
+        using MemoryStream stream = new();
+        PlanXmlIO.Save(plan, stream);
+        return Encoding.UTF8.GetString(stream.ToArray());
+    }
+
+    /// <summary>
+    /// Loads a plan from XML text.
+    /// </summary>
+    /// <param name="xml">The XML text to load.</param>
+    /// <returns>The loaded plan.</returns>
+    private static SongPlan LoadFromString(string xml) {
+        using MemoryStream stream = new(Encoding.UTF8.GetBytes(xml));
+        return PlanXmlIO.Load(stream);
+    }
+
+    /// <summary>
+    /// Saves and reloads a plan through an in-memory stream.
+    /// </summary>
+    /// <param name="plan">The plan to round-trip.</param>
+    /// <returns>The reloaded plan.</returns>
+    private static SongPlan RoundTrip(SongPlan plan) {
+        using MemoryStream stream = new();
+        PlanXmlIO.Save(plan, stream);
+        stream.Position = 0;
+        return PlanXmlIO.Load(stream);
+    }
+
+    /// <summary>
+    /// Asserts that two plan items contain the same field values.
+    /// </summary>
+    /// <param name="expected">The expected item.</param>
+    /// <param name="actual">The actual item.</param>
+    private static void AssertPlanItem(PlanItem expected, PlanItem actual) {
+        Assert.AreEqual(expected.Path, actual.Path);
+        Assert.AreEqual(expected.Artist, actual.Artist);
+        Assert.AreEqual(expected.Title, actual.Title);
+        Assert.AreEqual(expected.Comment, actual.Comment);
+    }
+}
diff --git a/SongTidy/Models/PlanItem.cs b/SongTidy/Models/PlanItem.cs
new file mode 100644
index 0000000..545a2fc
--- /dev/null
+++ b/SongTidy/Models/PlanItem.cs
@@ -0,0 +1,32 @@
+using System.Xml.Serialization;
+
+namespace SongTidy.Models;
+
+/// <summary>
+/// Represents one file entry stored in a plan document.
+/// </summary>
+public sealed class PlanItem {
+    /// <summary>
+    /// Gets or sets the absolute source file path.
+    /// </summary>
+    [XmlAttribute("Path")]
+    public string Path { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the artist value.
+    /// </summary>
+    [XmlAttribute("Artist")]
+    public string Artist { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the title value.
+    /// </summary>
+    [XmlAttribute("Title")]
+    public string Title { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the comment value.
+    /// </summary>
+    [XmlAttribute("Comment")]
+    public string Comment { get; set; } = string.Empty;
+}
diff --git a/SongTidy/Models/SongPlan.cs b/SongTidy/Models/SongPlan.cs
new file mode 100644
index 0000000..df4c275
--- /dev/null
+++ b/SongTidy/Models/SongPlan.cs
@@ -0,0 +1,34 @@
+using System.Collections.Generic;
+using System.Xml.Serialization;
+
+namespace SongTidy.Models;
+
+/// <summary>
+/// Represents a saved plan document containing the selected format and all entries.
+/// </summary>
+[XmlRoot("Plan")]
+public sealed class SongPlan {
+    /// <summary>
+    /// The plan file version written for new plans.
+    /// </summary>
+    public const int CurrentVersion = 1;
+
+    /// <summary>
+    /// Gets or sets the plan file version.
+    /// </summary>
+    [XmlAttribute("version")]
+    public int Version { get; set; } = CurrentVersion;
+
+    /// <summary>
+    /// Gets or sets the naming format used by the plan.
+    /// </summary>
+    [XmlElement("Format")]
+    public RenameFormat Format { get; set; } = RenameFormat.ArtistFirst;
+
+    /// <summary>
+    /// Gets or sets the entries stored in the plan.
+    /// </summary>
+    [XmlArray("Items")]
+    [XmlArrayItem("Item")]
+    public List<PlanItem> Items { get; set; } = new();
+}
diff --git a/SongTidy/Services/PlanXmlIO.cs b/SongTidy/Services/PlanXmlIO.cs
new file mode 100644
index 0000000..9be50de
--- /dev/null
+++ b/SongTidy/Services/PlanXmlIO.cs
@@ -0,0 +1,105 @@
+using System.IO;
+using System.Text;
+using System.Xml;
+using System.Xml.Serialization;
+
+using SongTidy.Models;
+
+namespace SongTidy.Services;
+
+/// <summary>
+/// Reads and writes plan documents in the application's XML format.
+/// </summary>
+public static class PlanXmlIO {
+    #region Stream access
+
+    /// <summary>
+    /// Writes a plan to a stream as UTF-8 XML.
+    /// </summary>
+    /// <param name="plan">The plan to write.</param>
+    /// <param name="stream">The destination stream. The stream is left open.</param>
+    public static void Save(SongPlan plan, Stream stream) {
+        XmlSerializer serializer = new(typeof(SongPlan));
+
+        // Suppress xsi and xsd namespace attributes to keep the plan file compact.
+        XmlSerializerNamespaces namespaces = new();
+        namespaces.Add(string.Empty, string.Empty);
+
+        using XmlWriter writer = XmlWriter.Create(stream, CreateWriterSettings());
+        serializer.Serialize(writer, plan, namespaces);
+    }
+
+    /// <summary>
+    /// Reads a plan from a stream.
+    /// </summary>
+    /// <param name="stream">The source stream. The stream is left open.</param>
+    /// <returns>The deserialized plan.</returns>
+    /// <exception cref="InvalidDataException">The document does not contain a plan.</exception>
+    public static SongPlan Load(Stream stream) {
+        XmlSerializer serializer = new(typeof(SongPlan));
+
+        using XmlReader reader = XmlReader.Create(stream, CreateReaderSettings());
+        SongPlan? plan = (SongPlan?)serializer.Deserialize(reader);
+
+        if (plan is null) {
+            throw new InvalidDataException("The XML document does not contain a plan.");
+        }
+
+        return plan;
+    }
+
+    #endregion
+
+    #region File access
+
+    /// <summary>
+    /// Writes a plan to a UTF-8 XML file, overwriting an existing file.
+    /// </summary>
+    /// <param name="plan">The plan to write.</param>
+    /// <param name="filePath">The destination file path.</param>
+    public static void Save(SongPlan plan, string filePath) {
+        using FileStream stream = new(filePath, FileMode.Create, FileAccess.Write, FileShare.None);
+        Save(plan, stream);
+    }
+
+    /// <summary>
+    /// Reads a plan from an XML file.
+    /// </summary>
+    /// <param name="filePath">The source file path.</param>
+    /// <returns>The deserialized plan.</returns>
+    public static SongPlan Load(string filePath) {
+        using FileStream stream = new(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);
+        return Load(stream);
+    }
+
+    #endregion
+
+    #region Helpers
+
+    /// <summary>
+    /// Creates the XML writer settings used for plan files.
+    /// </summary>
+    /// <returns>Writer settings that produce readable UTF-8 XML without a byte order mark.</returns>
+    private static XmlWriterSettings CreateWriterSettings() {
+        return new XmlWriterSettings {
+            Encoding = new UTF8Encoding(encoderShouldEmitUTF8Identifier: false),
+            Indent = true,
+            IndentChars = "  ",
+            CloseOutput = false,
+        };
+    }
+
+    /// <summary>
+    /// Creates the XML reader settings used for plan files.
+    /// </summary>
+    /// <returns>Reader settings that prohibit DTD processing and leave the input stream open.</returns>
+    private static XmlReaderSettings CreateReaderSettings() {
+        return new XmlReaderSettings {
+            DtdProcessing = DtdProcessing.Prohibit,
+            XmlResolver = null,
+            CloseInput = false,
+        };
+    }
+
+    #endregion
+}