diff --git a/docx-core/src/documents/elements/level.rs b/docx-core/src/documents/elements/level.rs
index aa43456..414fbdf 100644
--- a/docx-core/src/documents/elements/level.rs
+++ b/docx-core/src/documents/elements/level.rs
@@ -9,7 +9,7 @@ pub struct Level<'a> {
     format: NumberFormat<'a>,
     text: LevelText<'a>,
     jc: LevelJc<'a>,
-    paragraph_property: ParagraphProperty<'a>,
+    paragraph_property: ParagraphProperty,
 }
 
 impl<'a> Level<'a> {
diff --git a/docx-core/src/documents/elements/numbering.rs b/docx-core/src/documents/elements/numbering.rs
index 29a5c11..afd4fd3 100644
--- a/docx-core/src/documents/elements/numbering.rs
+++ b/docx-core/src/documents/elements/numbering.rs
@@ -3,12 +3,12 @@ use crate::xml_builder::*;
 
 #[derive(Debug, Clone)]
 pub struct Numbering<'a> {
-    id: &'a str,
+    id: usize,
     levels: Vec<Level<'a>>,
 }
 
 impl<'a> Numbering<'a> {
-    pub fn new(id: &'a str) -> Self {
+    pub fn new(id: usize) -> Self {
         Self { id, levels: vec![] }
     }
 
@@ -20,16 +20,13 @@ impl<'a> Numbering<'a> {
 
 impl<'a> BuildXML for Numbering<'a> {
     fn build(&self) -> Vec<u8> {
+        let id = format!("{}", self.id);
         let mut b = XMLBuilder::new();
-        b = b.open_abstract_num(self.id);
+        b = b.open_abstract_num(&id);
         for l in &self.levels {
             b = b.add_child(l);
         }
-        b.close()
-            .open_num(self.id)
-            .abstract_num_id(self.id)
-            .close()
-            .build()
+        b.close().open_num(&id).abstract_num_id(&id).close().build()
     }
 }
 
@@ -44,7 +41,7 @@ mod tests {
 
     #[test]
     fn test_numbering() {
-        let mut c = Numbering::new("0");
+        let mut c = Numbering::new(0);
         c = c.add_level(Level::new(
             1,
             Start::new(1),
diff --git a/docx-core/src/documents/elements/numbering_id.rs b/docx-core/src/documents/elements/numbering_id.rs
index 933e289..af48517 100644
--- a/docx-core/src/documents/elements/numbering_id.rs
+++ b/docx-core/src/documents/elements/numbering_id.rs
@@ -2,17 +2,17 @@ use crate::documents::BuildXML;
 use crate::xml_builder::*;
 
 #[derive(Debug, Clone)]
-pub struct NumberingId<'a> {
-    id: &'a str,
+pub struct NumberingId {
+    id: usize,
 }
 
-impl<'a> NumberingId<'a> {
-    pub fn new(id: &'a str) -> NumberingId<'a> {
+impl NumberingId {
+    pub fn new(id: usize) -> NumberingId {
         NumberingId { id }
     }
 }
 
-impl<'a> BuildXML for NumberingId<'a> {
+impl BuildXML for NumberingId {
     fn build(&self) -> Vec<u8> {
         let b = XMLBuilder::new();
         b.num_id(self.id).build()
@@ -29,8 +29,8 @@ mod tests {
 
     #[test]
     fn test_num_id() {
-        let c = NumberingId::new("abc");
+        let c = NumberingId::new(0);
         let b = c.build();
-        assert_eq!(str::from_utf8(&b).unwrap(), r#"<w:numId w:val="abc" />"#);
+        assert_eq!(str::from_utf8(&b).unwrap(), r#"<w:numId w:val="0" />"#);
     }
 }
diff --git a/docx-core/src/documents/elements/numbering_property.rs b/docx-core/src/documents/elements/numbering_property.rs
index 4856832..627a53e 100644
--- a/docx-core/src/documents/elements/numbering_property.rs
+++ b/docx-core/src/documents/elements/numbering_property.rs
@@ -3,18 +3,18 @@ use crate::documents::BuildXML;
 use crate::xml_builder::*;
 
 #[derive(Debug, Clone)]
-pub struct NumberingProperty<'a> {
-    id: NumberingId<'a>,
+pub struct NumberingProperty {
+    id: NumberingId,
     level: IndentLevel,
 }
 
-impl<'a> NumberingProperty<'a> {
-    pub fn new(id: NumberingId<'a>, level: IndentLevel) -> NumberingProperty {
+impl NumberingProperty {
+    pub fn new(id: NumberingId, level: IndentLevel) -> NumberingProperty {
         Self { id, level }
     }
 }
 
-impl<'a> BuildXML for NumberingProperty<'a> {
+impl BuildXML for NumberingProperty {
     fn build(&self) -> Vec<u8> {
         let b = XMLBuilder::new();
         b.open_numbering_property()
@@ -35,11 +35,11 @@ mod tests {
 
     #[test]
     fn test_num_property() {
-        let c = NumberingProperty::new(NumberingId::new("abc"), IndentLevel::new(3));
+        let c = NumberingProperty::new(NumberingId::new(0), IndentLevel::new(3));
         let b = c.build();
         assert_eq!(
             str::from_utf8(&b).unwrap(),
-            r#"<w:numPr><w:numId w:val="abc" /><w:ilvl w:val="3" /></w:numPr>"#
+            r#"<w:numPr><w:numId w:val="0" /><w:ilvl w:val="3" /></w:numPr>"#
         );
     }
 }
diff --git a/docx-core/src/documents/elements/paragraph.rs b/docx-core/src/documents/elements/paragraph.rs
index 62122ae..5d59c1a 100644
--- a/docx-core/src/documents/elements/paragraph.rs
+++ b/docx-core/src/documents/elements/paragraph.rs
@@ -6,7 +6,7 @@ use crate::xml_builder::*;
 #[derive(Debug, Clone)]
 pub struct Paragraph<'a> {
     pub(crate) children: Vec<ParagraphChild<'a>>,
-    property: ParagraphProperty<'a>,
+    property: ParagraphProperty,
     attrs: Vec<(String, String)>,
 }
 
@@ -119,7 +119,7 @@ impl<'a> Paragraph<'a> {
         self
     }
 
-    pub fn numbering(mut self, id: NumberingId<'a>, level: IndentLevel) -> Self {
+    pub fn numbering(mut self, id: NumberingId, level: IndentLevel) -> Self {
         self.property = self.property.numbering(id, level);
         self
     }
@@ -205,11 +205,11 @@ mod tests {
     fn test_numbering() {
         let b = Paragraph::new()
             .add_run(Run::new().add_text("Hello"))
-            .numbering(NumberingId::new("abc"), IndentLevel::new(1))
+            .numbering(NumberingId::new(0), IndentLevel::new(1))
             .build();
         assert_eq!(
             str::from_utf8(&b).unwrap(),
-            r#"<w:p><w:pPr><w:pStyle w:val="Normal" /><w:rPr /><w:numPr><w:numId w:val="abc" /><w:ilvl w:val="1" /></w:numPr></w:pPr><w:r><w:rPr /><w:t xml:space="preserve">Hello</w:t></w:r></w:p>"#
+            r#"<w:p><w:pPr><w:pStyle w:val="Normal" /><w:rPr /><w:numPr><w:numId w:val="0" /><w:ilvl w:val="1" /></w:numPr></w:pPr><w:r><w:rPr /><w:t xml:space="preserve">Hello</w:t></w:r></w:p>"#
         );
     }
 }
diff --git a/docx-core/src/documents/elements/paragraph_property.rs b/docx-core/src/documents/elements/paragraph_property.rs
index e42dec3..eb688f0 100644
--- a/docx-core/src/documents/elements/paragraph_property.rs
+++ b/docx-core/src/documents/elements/paragraph_property.rs
@@ -6,15 +6,15 @@ use crate::types::{AlignmentType, SpecialIndentType};
 use crate::xml_builder::*;
 
 #[derive(Debug, Clone)]
-pub struct ParagraphProperty<'a> {
+pub struct ParagraphProperty {
     run_property: RunProperty,
     style: ParagraphStyle,
-    numbering_property: Option<NumberingProperty<'a>>,
+    numbering_property: Option<NumberingProperty>,
     alignment: Option<Justification>,
     indent: Option<Indent>,
 }
 
-impl<'a> Default for ParagraphProperty<'a> {
+impl Default for ParagraphProperty {
     fn default() -> Self {
         let s: Option<&str> = None;
         ParagraphProperty {
@@ -32,8 +32,8 @@ impl<'a> Default for ParagraphProperty<'a> {
 // This element specifies a set of paragraph properties which shall be applied to the contents of the parent
 // paragraph after all style/numbering/table properties have been applied to the text. These properties are defined
 // as direct formatting, since they are directly applied to the paragraph and supersede any formatting from styles.
-impl<'a> ParagraphProperty<'a> {
-    pub fn new() -> ParagraphProperty<'a> {
+impl ParagraphProperty {
+    pub fn new() -> ParagraphProperty {
         Default::default()
     }
 
@@ -52,13 +52,13 @@ impl<'a> ParagraphProperty<'a> {
         self
     }
 
-    pub fn numbering(mut self, id: NumberingId<'a>, level: IndentLevel) -> Self {
+    pub fn numbering(mut self, id: NumberingId, level: IndentLevel) -> Self {
         self.numbering_property = Some(NumberingProperty::new(id, level));
         self
     }
 }
 
-impl<'a> BuildXML for ParagraphProperty<'a> {
+impl BuildXML for ParagraphProperty {
     fn build(&self) -> Vec<u8> {
         XMLBuilder::new()
             .open_paragraph_property()
diff --git a/docx-core/src/documents/elements/style.rs b/docx-core/src/documents/elements/style.rs
index 7fef5b8..313d29d 100644
--- a/docx-core/src/documents/elements/style.rs
+++ b/docx-core/src/documents/elements/style.rs
@@ -5,15 +5,15 @@ use crate::StyleType;
 use super::{BasedOn, Name, Next, ParagraphProperty, QFormat, RunProperty};
 
 #[derive(Debug)]
-pub struct Style<'a> {
+pub struct Style {
     style_id: String,
     name: Name,
     style_type: StyleType,
     run_property: RunProperty,
-    paragraph_property: ParagraphProperty<'a>,
+    paragraph_property: ParagraphProperty,
 }
 
-impl<'a> Default for Style<'a> {
+impl Default for Style {
     fn default() -> Self {
         let name = Name::new("");
         let rpr = RunProperty::new();
@@ -28,7 +28,7 @@ impl<'a> Default for Style<'a> {
     }
 }
 
-impl<'a> Style<'a> {
+impl Style {
     pub fn new(
         style_id: impl Into<String>,
         name: impl Into<String>,
@@ -65,7 +65,7 @@ impl<'a> Style<'a> {
     }
 }
 
-impl<'a> BuildXML for Style<'a> {
+impl BuildXML for Style {
     fn build(&self) -> Vec<u8> {
         let b = XMLBuilder::new();
         // Set "Normal" as default if you need change these values please fix it
diff --git a/docx-core/src/documents/mod.rs b/docx-core/src/documents/mod.rs
index c1b61b9..975d32c 100644
--- a/docx-core/src/documents/mod.rs
+++ b/docx-core/src/documents/mod.rs
@@ -35,7 +35,7 @@ pub struct Docx<'a> {
     rels: Rels,
     document_rels: DocumentRels,
     doc_props: DocProps<'a>,
-    styles: Styles<'a>,
+    styles: Styles,
     document: Document<'a>,
     comments: Comments<'a>,
     numberings: Numberings<'a>,
diff --git a/docx-core/src/documents/numberings.rs b/docx-core/src/documents/numberings.rs
index 2f7e5d0..3afd65d 100644
--- a/docx-core/src/documents/numberings.rs
+++ b/docx-core/src/documents/numberings.rs
@@ -37,7 +37,7 @@ impl<'a> BuildXML for Numberings<'a> {
 }
 
 fn create_default_numbering() -> Numbering<'static> {
-    Numbering::new("0")
+    Numbering::new(0)
         .add_level(
             Level::new(
                 0,
diff --git a/docx-core/src/documents/styles.rs b/docx-core/src/documents/styles.rs
index 79607b3..66edbdc 100644
--- a/docx-core/src/documents/styles.rs
+++ b/docx-core/src/documents/styles.rs
@@ -4,23 +4,23 @@ use crate::types::*;
 use crate::xml_builder::*;
 
 #[derive(Debug)]
-pub struct Styles<'a> {
+pub struct Styles {
     doc_defaults: DocDefaults,
-    styles: Vec<Style<'a>>,
+    styles: Vec<Style>,
 }
 
-impl<'a> Styles<'a> {
-    pub fn new() -> Styles<'a> {
+impl Styles {
+    pub fn new() -> Styles {
         Default::default()
     }
 
-    pub fn add_style(mut self, style: Style<'a>) -> Self {
+    pub fn add_style(mut self, style: Style) -> Self {
         self.styles.push(style);
         self
     }
 }
 
-impl<'a> Default for Styles<'a> {
+impl Default for Styles {
     fn default() -> Self {
         Self {
             doc_defaults: DocDefaults::new(),
@@ -29,7 +29,7 @@ impl<'a> Default for Styles<'a> {
     }
 }
 
-impl<'a> BuildXML for Styles<'a> {
+impl BuildXML for Styles {
     fn build(&self) -> Vec<u8> {
         let b = XMLBuilder::new();
         let normal = Style::new("Normal", "Normal", StyleType::Paragraph);
diff --git a/docx-core/src/xml_builder/elements.rs b/docx-core/src/xml_builder/elements.rs
index bfea251..632809b 100644
--- a/docx-core/src/xml_builder/elements.rs
+++ b/docx-core/src/xml_builder/elements.rs
@@ -191,7 +191,7 @@ impl XMLBuilder {
     opened_el!(open_num, "w:num", "w:numId");
     opened_el!(open_numbering_property, "w:numPr");
     only_usize_val_el!(indent_level, "w:ilvl");
-    only_str_val_el!(num_id, "w:numId");
+    only_usize_val_el!(num_id, "w:numId");
     only_usize_val_el!(start, "w:start");
     only_str_val_el!(number_format, "w:numFmt");
     only_str_val_el!(level_text, "w:lvlText");
diff --git a/docx-core/tests/lib.rs b/docx-core/tests/lib.rs
index dd1afdc..dc19c29 100644
--- a/docx-core/tests/lib.rs
+++ b/docx-core/tests/lib.rs
@@ -323,22 +323,49 @@ pub fn default_numbering() -> Result<(), DocxError> {
     .add_paragraph(
       Paragraph::new()
         .add_run(Run::new().add_text("Hello"))
-        .numbering(NumberingId::new("0"), IndentLevel::new(0)),
+        .numbering(NumberingId::new(0), IndentLevel::new(0)),
     )
     .add_paragraph(
       Paragraph::new()
         .add_run(Run::new().add_text("World!"))
-        .numbering(NumberingId::new("0"), IndentLevel::new(1)),
+        .numbering(NumberingId::new(0), IndentLevel::new(1)),
     )
     .add_paragraph(
       Paragraph::new()
         .add_run(Run::new().add_text("Foooo!"))
-        .numbering(NumberingId::new("0"), IndentLevel::new(2)),
+        .numbering(NumberingId::new(0), IndentLevel::new(2)),
     )
     .add_paragraph(
       Paragraph::new()
         .add_run(Run::new().add_text("Bar!"))
-        .numbering(NumberingId::new("0"), IndentLevel::new(3)),
+        .numbering(NumberingId::new(0), IndentLevel::new(3)),
+    )
+    .build()
+    .pack(file)?;
+  Ok(())
+}
+
+#[test]
+pub fn user_numbering() -> Result<(), DocxError> {
+  let path = std::path::Path::new("./tests/output/user_numbering.docx");
+  let file = std::fs::File::create(&path).unwrap();
+  Docx::new()
+    .add_paragraph(
+      Paragraph::new()
+        .add_run(Run::new().add_text("Hello"))
+        .numbering(NumberingId::new(2), IndentLevel::new(0)),
+    )
+    .add_numbering(
+      Numbering::new(2).add_level(
+        Level::new(
+          0,
+          Start::new(1),
+          NumberFormat::new("decimal"),
+          LevelText::new("Section %1."),
+          LevelJc::new("left"),
+        )
+        .indent(1620, Some(SpecialIndentType::Hanging(320))),
+      ),
     )
     .build()
     .pack(file)?;