diff --git a/news/10159.trivial.rst b/news/10159.trivial.rst
new file mode 100644
index 00000000000..f52e7baeb19
--- /dev/null
+++ b/news/10159.trivial.rst
@@ -0,0 +1 @@
+Complete the type annotations from ``pip/_internal/utils``.
diff --git a/src/pip/_internal/utils/appdirs.py b/src/pip/_internal/utils/appdirs.py
index db974dad635..a8403b7dee4 100644
--- a/src/pip/_internal/utils/appdirs.py
+++ b/src/pip/_internal/utils/appdirs.py
@@ -12,13 +12,11 @@
 from pip._vendor import appdirs as _appdirs
 
 
-def user_cache_dir(appname):
-    # type: (str) -> str
+def user_cache_dir(appname: str) -> str:
     return _appdirs.user_cache_dir(appname, appauthor=False)
 
 
-def user_config_dir(appname, roaming=True):
-    # type: (str, bool) -> str
+def user_config_dir(appname: str, roaming: bool = True) -> str:
     path = _appdirs.user_config_dir(appname, appauthor=False, roaming=roaming)
     if _appdirs.system == "darwin" and not os.path.isdir(path):
         path = os.path.expanduser("~/.config/")
@@ -29,8 +27,7 @@ def user_config_dir(appname, roaming=True):
 
 # for the discussion regarding site_config_dir locations
 # see <https://github.com/pypa/pip/issues/1733>
-def site_config_dirs(appname):
-    # type: (str) -> List[str]
+def site_config_dirs(appname: str) -> List[str]:
     dirval = _appdirs.site_config_dir(appname, appauthor=False, multipath=True)
     if _appdirs.system not in ["win32", "darwin"]:
         # always look in /etc directly as well
diff --git a/src/pip/_internal/utils/compat.py b/src/pip/_internal/utils/compat.py
index 1fb2dc729e0..3f4d300cef0 100644
--- a/src/pip/_internal/utils/compat.py
+++ b/src/pip/_internal/utils/compat.py
@@ -11,8 +11,7 @@
 logger = logging.getLogger(__name__)
 
 
-def has_tls():
-    # type: () -> bool
+def has_tls() -> bool:
     try:
         import _ssl  # noqa: F401  # ignore unused
 
@@ -25,8 +24,7 @@ def has_tls():
     return IS_PYOPENSSL
 
 
-def get_path_uid(path):
-    # type: (str) -> int
+def get_path_uid(path: str) -> int:
     """
     Return path's uid.
 
diff --git a/src/pip/_internal/utils/compatibility_tags.py b/src/pip/_internal/utils/compatibility_tags.py
index 14fe51c1a51..f1c0f063370 100644
--- a/src/pip/_internal/utils/compatibility_tags.py
+++ b/src/pip/_internal/utils/compatibility_tags.py
@@ -21,14 +21,12 @@
 _osx_arch_pat = re.compile(r"(.+)_(\d+)_(\d+)_(.+)")
 
 
-def version_info_to_nodot(version_info):
-    # type: (Tuple[int, ...]) -> str
+def version_info_to_nodot(version_info: Tuple[int, ...]) -> str:
     # Only use up to the first two numbers.
     return "".join(map(str, version_info[:2]))
 
 
-def _mac_platforms(arch):
-    # type: (str) -> List[str]
+def _mac_platforms(arch: str) -> List[str]:
     match = _osx_arch_pat.match(arch)
     if match:
         name, major, minor, actual_arch = match.groups()
@@ -48,8 +46,7 @@ def _mac_platforms(arch):
     return arches
 
 
-def _custom_manylinux_platforms(arch):
-    # type: (str) -> List[str]
+def _custom_manylinux_platforms(arch: str) -> List[str]:
     arches = [arch]
     arch_prefix, arch_sep, arch_suffix = arch.partition("_")
     if arch_prefix == "manylinux2014":
@@ -70,8 +67,7 @@ def _custom_manylinux_platforms(arch):
     return arches
 
 
-def _get_custom_platforms(arch):
-    # type: (str) -> List[str]
+def _get_custom_platforms(arch: str) -> List[str]:
     arch_prefix, arch_sep, arch_suffix = arch.partition("_")
     if arch.startswith("macosx"):
         arches = _mac_platforms(arch)
@@ -82,8 +78,7 @@ def _get_custom_platforms(arch):
     return arches
 
 
-def _expand_allowed_platforms(platforms):
-    # type: (Optional[List[str]]) -> Optional[List[str]]
+def _expand_allowed_platforms(platforms: Optional[List[str]]) -> Optional[List[str]]:
     if not platforms:
         return None
 
@@ -100,16 +95,16 @@ def _expand_allowed_platforms(platforms):
     return result
 
 
-def _get_python_version(version):
-    # type: (str) -> PythonVersion
+def _get_python_version(version: str) -> "PythonVersion":
     if len(version) > 1:
         return int(version[0]), int(version[1:])
     else:
         return (int(version[0]),)
 
 
-def _get_custom_interpreter(implementation=None, version=None):
-    # type: (Optional[str], Optional[str]) -> str
+def _get_custom_interpreter(
+    implementation: Optional[str] = None, version: Optional[str] = None
+) -> str:
     if implementation is None:
         implementation = interpreter_name()
     if version is None:
@@ -118,12 +113,11 @@ def _get_custom_interpreter(implementation=None, version=None):
 
 
 def get_supported(
-    version=None,  # type: Optional[str]
-    platforms=None,  # type: Optional[List[str]]
-    impl=None,  # type: Optional[str]
-    abis=None,  # type: Optional[List[str]]
-):
-    # type: (...) -> List[Tag]
+    version: Optional[str] = None,
+    platforms: Optional[List[str]] = None,
+    impl: Optional[str] = None,
+    abis: Optional[List[str]] = None,
+) -> List[Tag]:
     """Return a list of supported tags for each version specified in
     `versions`.
 
@@ -136,9 +130,9 @@ def get_supported(
     :param abis: specify a list of abis you want valid
         tags for, or None. If None, use the local interpreter abi.
     """
-    supported = []  # type: List[Tag]
+    supported: List[Tag] = []
 
-    python_version = None  # type: Optional[PythonVersion]
+    python_version: Optional["PythonVersion"] = None
     if version is not None:
         python_version = _get_python_version(version)
 
diff --git a/src/pip/_internal/utils/datetime.py b/src/pip/_internal/utils/datetime.py
index b638646c8bb..8668b3b0ec1 100644
--- a/src/pip/_internal/utils/datetime.py
+++ b/src/pip/_internal/utils/datetime.py
@@ -4,8 +4,7 @@
 import datetime
 
 
-def today_is_later_than(year, month, day):
-    # type: (int, int, int) -> bool
+def today_is_later_than(year: int, month: int, day: int) -> bool:
     today = datetime.date.today()
     given = datetime.date(year, month, day)
 
diff --git a/src/pip/_internal/utils/deprecation.py b/src/pip/_internal/utils/deprecation.py
index b62b3fb6509..57dbdbdca4e 100644
--- a/src/pip/_internal/utils/deprecation.py
+++ b/src/pip/_internal/utils/deprecation.py
@@ -17,19 +17,18 @@ class PipDeprecationWarning(Warning):
     pass
 
 
-_original_showwarning = None  # type: Any
+_original_showwarning: Any = None
 
 
 # Warnings <-> Logging Integration
 def _showwarning(
-    message,  # type: Union[Warning, str]
-    category,  # type: Type[Warning]
-    filename,  # type: str
-    lineno,  # type: int
-    file=None,  # type: Optional[TextIO]
-    line=None,  # type: Optional[str]
-):
-    # type: (...) -> None
+    message: Union[Warning, str],
+    category: Type[Warning],
+    filename: str,
+    lineno: int,
+    file: Optional[TextIO] = None,
+    line: Optional[str] = None,
+) -> None:
     if file is not None:
         if _original_showwarning is not None:
             _original_showwarning(message, category, filename, lineno, file, line)
@@ -42,8 +41,7 @@ def _showwarning(
         _original_showwarning(message, category, filename, lineno, file, line)
 
 
-def install_warning_logger():
-    # type: () -> None
+def install_warning_logger() -> None:
     # Enable our Deprecation Warnings
     warnings.simplefilter("default", PipDeprecationWarning, append=True)
 
@@ -54,8 +52,12 @@ def install_warning_logger():
         warnings.showwarning = _showwarning
 
 
-def deprecated(reason, replacement, gone_in, issue=None):
-    # type: (str, Optional[str], Optional[str], Optional[int]) -> None
+def deprecated(
+    reason: str,
+    replacement: Optional[str],
+    gone_in: Optional[str],
+    issue: Optional[int] = None,
+) -> None:
     """Helper to deprecate existing functionality.
 
     reason:
diff --git a/src/pip/_internal/utils/direct_url_helpers.py b/src/pip/_internal/utils/direct_url_helpers.py
index 359a9db16b5..088e977b5b1 100644
--- a/src/pip/_internal/utils/direct_url_helpers.py
+++ b/src/pip/_internal/utils/direct_url_helpers.py
@@ -5,8 +5,7 @@
 from pip._internal.vcs import vcs
 
 
-def direct_url_as_pep440_direct_reference(direct_url, name):
-    # type: (DirectUrl, str) -> str
+def direct_url_as_pep440_direct_reference(direct_url: DirectUrl, name: str) -> str:
     """Convert a DirectUrl to a pip requirement string."""
     direct_url.validate()  # if invalid, this is a pip bug
     requirement = name + " @ "
@@ -29,8 +28,9 @@ def direct_url_as_pep440_direct_reference(direct_url, name):
     return requirement
 
 
-def direct_url_from_link(link, source_dir=None, link_is_in_wheel_cache=False):
-    # type: (Link, Optional[str], bool) -> DirectUrl
+def direct_url_from_link(
+    link: Link, source_dir: Optional[str] = None, link_is_in_wheel_cache: bool = False
+) -> DirectUrl:
     if link.is_vcs:
         vcs_backend = vcs.get_backend_for_scheme(link.scheme)
         assert vcs_backend
diff --git a/src/pip/_internal/utils/distutils_args.py b/src/pip/_internal/utils/distutils_args.py
index e886c8884d0..e4aa5b827f6 100644
--- a/src/pip/_internal/utils/distutils_args.py
+++ b/src/pip/_internal/utils/distutils_args.py
@@ -22,8 +22,7 @@
 _distutils_getopt = FancyGetopt(_options)  # type: ignore
 
 
-def parse_distutils_args(args):
-    # type: (List[str]) -> Dict[str, str]
+def parse_distutils_args(args: List[str]) -> Dict[str, str]:
     """Parse provided arguments, returning an object that has the
     matched arguments.
 
diff --git a/src/pip/_internal/utils/encoding.py b/src/pip/_internal/utils/encoding.py
index 7c8893d559e..1c73f6c9a5d 100644
--- a/src/pip/_internal/utils/encoding.py
+++ b/src/pip/_internal/utils/encoding.py
@@ -4,7 +4,7 @@
 import sys
 from typing import List, Tuple
 
-BOMS = [
+BOMS: List[Tuple[bytes, str]] = [
     (codecs.BOM_UTF8, "utf-8"),
     (codecs.BOM_UTF16, "utf-16"),
     (codecs.BOM_UTF16_BE, "utf-16-be"),
@@ -12,13 +12,12 @@
     (codecs.BOM_UTF32, "utf-32"),
     (codecs.BOM_UTF32_BE, "utf-32-be"),
     (codecs.BOM_UTF32_LE, "utf-32-le"),
-]  # type: List[Tuple[bytes, str]]
+]
 
 ENCODING_RE = re.compile(br"coding[:=]\s*([-\w.]+)")
 
 
-def auto_decode(data):
-    # type: (bytes) -> str
+def auto_decode(data: bytes) -> str:
     """Check a bytes string for a BOM to correctly detect the encoding
 
     Fallback to locale.getpreferredencoding(False) like open() on Python3"""
diff --git a/src/pip/_internal/utils/entrypoints.py b/src/pip/_internal/utils/entrypoints.py
index 879bf21ac5f..1504a12916b 100644
--- a/src/pip/_internal/utils/entrypoints.py
+++ b/src/pip/_internal/utils/entrypoints.py
@@ -4,8 +4,7 @@
 from pip._internal.cli.main import main
 
 
-def _wrapper(args=None):
-    # type: (Optional[List[str]]) -> int
+def _wrapper(args: Optional[List[str]] = None) -> int:
     """Central wrapper for all old entrypoints.
 
     Historically pip has had several entrypoints defined. Because of issues
diff --git a/src/pip/_internal/utils/filesystem.py b/src/pip/_internal/utils/filesystem.py
index 177a6b4fbb5..b7e6191abe6 100644
--- a/src/pip/_internal/utils/filesystem.py
+++ b/src/pip/_internal/utils/filesystem.py
@@ -15,8 +15,7 @@
 from pip._internal.utils.misc import format_size
 
 
-def check_path_owner(path):
-    # type: (str) -> bool
+def check_path_owner(path: str) -> bool:
     # If we don't have a way to check the effective uid of this process, then
     # we'll just assume that we own the directory.
     if sys.platform == "win32" or not hasattr(os, "geteuid"):
@@ -43,8 +42,7 @@ def check_path_owner(path):
     return False  # assume we don't own the path
 
 
-def copy2_fixed(src, dest):
-    # type: (str, str) -> None
+def copy2_fixed(src: str, dest: str) -> None:
     """Wrap shutil.copy2() but map errors copying socket files to
     SpecialFileError as expected.
 
@@ -67,14 +65,12 @@ def copy2_fixed(src, dest):
         raise
 
 
-def is_socket(path):
-    # type: (str) -> bool
+def is_socket(path: str) -> bool:
     return stat.S_ISSOCK(os.lstat(path).st_mode)
 
 
 @contextmanager
-def adjacent_tmp_file(path, **kwargs):
-    # type: (str, **Any) -> Iterator[BinaryIO]
+def adjacent_tmp_file(path: str, **kwargs: Any) -> Iterator[BinaryIO]:
     """Return a file-like object pointing to a tmp file next to path.
 
     The file is created securely and is ensured to be written to disk
@@ -106,8 +102,7 @@ def adjacent_tmp_file(path, **kwargs):
 
 # test_writable_dir and _test_writable_dir_win are copied from Flit,
 # with the author's agreement to also place them under pip's license.
-def test_writable_dir(path):
-    # type: (str) -> bool
+def test_writable_dir(path: str) -> bool:
     """Check if a directory is writable.
 
     Uses os.access() on POSIX, tries creating files on Windows.
@@ -125,8 +120,7 @@ def test_writable_dir(path):
     return _test_writable_dir_win(path)
 
 
-def _test_writable_dir_win(path):
-    # type: (str) -> bool
+def _test_writable_dir_win(path: str) -> bool:
     # os.access doesn't work on Windows: http://bugs.python.org/issue2528
     # and we can't use tempfile: http://bugs.python.org/issue22107
     basename = "accesstest_deleteme_fishfingers_custard_"
@@ -154,32 +148,28 @@ def _test_writable_dir_win(path):
     raise OSError("Unexpected condition testing for writable directory")
 
 
-def find_files(path, pattern):
-    # type: (str, str) -> List[str]
+def find_files(path: str, pattern: str) -> List[str]:
     """Returns a list of absolute paths of files beneath path, recursively,
     with filenames which match the UNIX-style shell glob pattern."""
-    result = []  # type: List[str]
+    result: List[str] = []
     for root, _, files in os.walk(path):
         matches = fnmatch.filter(files, pattern)
         result.extend(os.path.join(root, f) for f in matches)
     return result
 
 
-def file_size(path):
-    # type: (str) -> Union[int, float]
+def file_size(path: str) -> Union[int, float]:
     # If it's a symlink, return 0.
     if os.path.islink(path):
         return 0
     return os.path.getsize(path)
 
 
-def format_file_size(path):
-    # type: (str) -> str
+def format_file_size(path: str) -> str:
     return format_size(file_size(path))
 
 
-def directory_size(path):
-    # type: (str) -> Union[int, float]
+def directory_size(path: str) -> Union[int, float]:
     size = 0.0
     for root, _dirs, files in os.walk(path):
         for filename in files:
@@ -188,6 +178,5 @@ def directory_size(path):
     return size
 
 
-def format_directory_size(path):
-    # type: (str) -> str
+def format_directory_size(path: str) -> str:
     return format_size(directory_size(path))