diff --git a/cmd/apply.go b/cmd/apply.go
index df369ff9..f1c6536f 100644
--- a/cmd/apply.go
+++ b/cmd/apply.go
@@ -42,8 +42,8 @@ func NewApplyCmd(globalCfg *config.GlobalImpl) *cobra.Command {
 	f.BoolVar(&applyOptions.DetailedExitcode, "detailed-exitcode", false, "return a non-zero exit code 2 instead of 0 when there were changes detected AND the changes are synced successfully")
 	f.StringVar(&globalCfg.GlobalOptions.Args, "args", "", "pass args to helm exec")
 	if !runtime.V1Mode {
+		// TODO: Remove this function once Helmfile v0.x
 		f.BoolVar(&applyOptions.RetainValuesFiles, "retain-values-files", false, "DEPRECATED: Use skip-cleanup instead")
-		// mark retain-values-files as deprecated, but keep it for backward compatibility, will be removed in the future
 		_ = f.MarkDeprecated("retain-values-files", "Use skip-cleanup instead")
 	}
 
diff --git a/cmd/charts.go b/cmd/charts.go
index 44c92207..1763f813 100644
--- a/cmd/charts.go
+++ b/cmd/charts.go
@@ -1,3 +1,4 @@
+// TODO: Remove this function once Helmfile v0.x
 package cmd
 
 import (
diff --git a/cmd/delete.go b/cmd/delete.go
index 1329bcaa..c39c8890 100644
--- a/cmd/delete.go
+++ b/cmd/delete.go
@@ -1,3 +1,4 @@
+// TODO: Remove this function once Helmfile v0.x
 package cmd
 
 import (
diff --git a/cmd/root.go b/cmd/root.go
index c3fd1d5b..b6c01a05 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -103,6 +103,7 @@ func NewRootCmd(globalConfig *config.GlobalOptions) (*cobra.Command, error) {
 		),
 	)
 
+	// TODO: Remove this function once Helmfile v0.x
 	if !runtime.V1Mode {
 		cmd.AddCommand(
 			NewChartsCmd(globalImpl),
diff --git a/pkg/app/app.go b/pkg/app/app.go
index 82ce75de..0473dca5 100644
--- a/pkg/app/app.go
+++ b/pkg/app/app.go
@@ -132,6 +132,7 @@ func (a *App) Repos(c ReposConfigProvider) error {
 	}, c.IncludeTransitiveNeeds(), SetFilter(true))
 }
 
+// TODO: Remove this function once Helmfile v0.x
 func (a *App) DeprecatedSyncCharts(c DeprecatedChartsConfigProvider) error {
 	return a.ForEachState(func(run *Run) (_ bool, errs []error) {
 		err := run.withPreparedCharts("charts", state.ChartPrepareOptions{
@@ -457,6 +458,7 @@ func (a *App) Status(c StatusesConfigProvider) error {
 	}, false, SetFilter(true))
 }
 
+// TODO: Remove this function once Helmfile v0.x
 func (a *App) Delete(c DeleteConfigProvider) error {
 	return a.ForEachState(func(run *Run) (ok bool, errs []error) {
 		err := run.withPreparedCharts("delete", state.ChartPrepareOptions{
@@ -1166,6 +1168,8 @@ func (a *App) findDesiredStateFiles(specifiedPath string, opts LoadOpts) ([]stri
 		var defaultFile string
 		if a.fs.FileExistsAt(DefaultHelmfile) {
 			defaultFile = DefaultHelmfile
+
+			// TODO: Remove this function once Helmfile v0.x
 		} else if a.fs.FileExistsAt(DeprecatedHelmfile) {
 			log.Printf(
 				"warn: %s is being loaded: %s is deprecated in favor of %s. See https://github.com/roboll/helmfile/issues/25 for more information",
diff --git a/pkg/app/app_test.go b/pkg/app/app_test.go
index 27a07cbd..ae0e8a67 100644
--- a/pkg/app/app_test.go
+++ b/pkg/app/app_test.go
@@ -2310,9 +2310,12 @@ func (c configImpl) PostRenderer() string {
 }
 
 type applyConfig struct {
-	args                   string
-	values                 []string
-	retainValuesFiles      bool
+	args   string
+	values []string
+
+	// TODO: Remove this function once Helmfile v0.x
+	retainValuesFiles bool
+
 	set                    []string
 	validate               bool
 	skipCleanup            bool
@@ -2450,6 +2453,7 @@ func (a applyConfig) Logger() *zap.SugaredLogger {
 	return a.logger
 }
 
+// TODO: Remove this function once Helmfile v0.x
 func (a applyConfig) RetainValuesFiles() bool {
 	return a.retainValuesFiles
 }
diff --git a/pkg/app/config.go b/pkg/app/config.go
index 4bf17d72..9379d4e8 100644
--- a/pkg/app/config.go
+++ b/pkg/app/config.go
@@ -19,6 +19,7 @@ type ConfigProvider interface {
 	loggingConfig
 }
 
+// TODO: Remove this function once Helmfile v0.x
 type DeprecatedChartsConfigProvider interface {
 	Values() []string
 
@@ -66,7 +67,9 @@ type ApplyConfigProvider interface {
 	Context() int
 	DiffOutput() string
 
+	// TODO: Remove this function once Helmfile v0.x
 	RetainValuesFiles() bool
+
 	Validate() bool
 	SkipCleanup() bool
 	SkipDiffOnInstall() bool
@@ -133,6 +136,7 @@ type DiffConfigProvider interface {
 	valuesControlMode
 }
 
+// TODO: Remove this function once Helmfile v0.x
 type DeleteConfigProvider interface {
 	Args() string
 
diff --git a/pkg/app/constants.go b/pkg/app/constants.go
index 38a75101..63fd3af7 100644
--- a/pkg/app/constants.go
+++ b/pkg/app/constants.go
@@ -8,8 +8,10 @@ import (
 )
 
 const (
-	DefaultHelmfile              = "helmfile.yaml"
-	DeprecatedHelmfile           = "charts.yaml"
+	DefaultHelmfile = "helmfile.yaml"
+	// TODO: Remove this function once Helmfile v0.x
+	DeprecatedHelmfile = "charts.yaml"
+
 	DefaultHelmfileDirectory     = "helmfile.d"
 	ExperimentalSelectorExplicit = "explicit-selector-inheritance" // value to remove default selector inheritance to sub-helmfiles and use the explicit one
 )
diff --git a/pkg/app/run.go b/pkg/app/run.go
index 8e349b16..af44ac7b 100644
--- a/pkg/app/run.go
+++ b/pkg/app/run.go
@@ -112,6 +112,7 @@ func (r *Run) Repos(c ReposConfigProvider) error {
 	return r.ctx.SyncReposOnce(r.state, r.helm)
 }
 
+// TODO: Remove this function once Helmfile v0.x
 func (r *Run) DeprecatedSyncCharts(c DeprecatedChartsConfigProvider) []error {
 	st := r.state
 	helm := r.helm
diff --git a/pkg/config/apply.go b/pkg/config/apply.go
index 47cdac34..4ab0296d 100644
--- a/pkg/config/apply.go
+++ b/pkg/config/apply.go
@@ -16,8 +16,11 @@ type ApplyOptions struct {
 	Output string
 	// DetailedExitcode is true if the exit code should be 2 instead of 0 if there were changes detected and the changes were synced successfully
 	DetailedExitcode bool
+
+	// TODO: Remove this function once Helmfile v0.x
 	// DEPRECATED: Use skip-cleanup instead
 	RetainValuesFiles bool
+
 	// SkipCleanup is true if the cleanup of temporary values files should be skipped
 	SkipCleanup bool
 	// SkipCRDs is true if the CRDs should be skipped
@@ -113,6 +116,7 @@ func (a *ApplyImpl) IncludeTransitiveNeeds() bool {
 	return a.ApplyOptions.IncludeTransitiveNeeds
 }
 
+// TODO: Remove this function once Helmfile v0.x
 // RetainValuesFiles returns the retain values files.
 func (a *ApplyImpl) RetainValuesFiles() bool {
 	return a.ApplyOptions.RetainValuesFiles
diff --git a/pkg/config/charts.go b/pkg/config/charts.go
index 00650beb..7319c5ac 100644
--- a/pkg/config/charts.go
+++ b/pkg/config/charts.go
@@ -1,3 +1,4 @@
+// TODO: Remove this function once Helmfile v0.x
 package config
 
 // ChartsOptions is the options for the build command
diff --git a/pkg/config/delete.go b/pkg/config/delete.go
index 5ef3be47..8b58a96a 100644
--- a/pkg/config/delete.go
+++ b/pkg/config/delete.go
@@ -1,3 +1,4 @@
+// TODO: Remove this function once Helmfile v0.x
 package config
 
 // DeleteOptions is the options for the build command
diff --git a/pkg/state/create.go b/pkg/state/create.go
index 6a8d9672..51074ce3 100644
--- a/pkg/state/create.go
+++ b/pkg/state/create.go
@@ -108,6 +108,7 @@ func (c *StateCreator) Parse(content []byte, baseDir, file string) (*HelmState,
 		}
 	}
 
+	// TODO: Remove this function once Helmfile v0.x
 	if len(state.DeprecatedReleases) > 0 {
 		if len(state.Releases) > 0 {
 			return nil, fmt.Errorf("failed to parse %s: you can't specify both `charts` and `releases` sections", file)
@@ -116,6 +117,7 @@ func (c *StateCreator) Parse(content []byte, baseDir, file string) (*HelmState,
 		state.DeprecatedReleases = []ReleaseSpec{}
 	}
 
+	// TODO: Remove this function once Helmfile v0.x
 	if state.DeprecatedContext != "" && state.HelmDefaults.KubeContext == "" {
 		state.HelmDefaults.KubeContext = state.DeprecatedContext
 	}
diff --git a/pkg/state/create_test.go b/pkg/state/create_test.go
index d60fde85..5983766f 100644
--- a/pkg/state/create_test.go
+++ b/pkg/state/create_test.go
@@ -279,6 +279,7 @@ func TestReadFromYaml_StrictUnmarshalling(t *testing.T) {
 	}
 }
 
+// TODO: Remove this function once Helmfile v0.x
 func TestReadFromYaml_DeprecatedReleaseReferences(t *testing.T) {
 	yamlFile := "example/path/to/yaml/file"
 	yamlContent := []byte(`charts:
diff --git a/pkg/state/state.go b/pkg/state/state.go
index 8ef6fef2..68f7ad39 100644
--- a/pkg/state/state.go
+++ b/pkg/state/state.go
@@ -49,11 +49,14 @@ type ReleaseSetSpec struct {
 
 	Environments map[string]EnvironmentSpec `yaml:"environments,omitempty"`
 
-	Bases               []string          `yaml:"bases,omitempty"`
-	HelmDefaults        HelmSpec          `yaml:"helmDefaults,omitempty"`
-	Helmfiles           []SubHelmfileSpec `yaml:"helmfiles,omitempty"`
-	DeprecatedContext   string            `yaml:"context,omitempty"`
-	DeprecatedReleases  []ReleaseSpec     `yaml:"charts,omitempty"`
+	Bases        []string          `yaml:"bases,omitempty"`
+	HelmDefaults HelmSpec          `yaml:"helmDefaults,omitempty"`
+	Helmfiles    []SubHelmfileSpec `yaml:"helmfiles,omitempty"`
+
+	// TODO: Remove this function once Helmfile v0.x
+	DeprecatedContext  string        `yaml:"context,omitempty"`
+	DeprecatedReleases []ReleaseSpec `yaml:"charts,omitempty"`
+
 	OverrideKubeContext string            `yaml:"kubeContext,omitempty"`
 	OverrideNamespace   string            `yaml:"namespace,omitempty"`
 	OverrideChart       string            `yaml:"chart,omitempty"`
diff --git a/pkg/state/state_test.go b/pkg/state/state_test.go
index 76fe931b..9326c490 100644
--- a/pkg/state/state_test.go
+++ b/pkg/state/state_test.go
@@ -54,12 +54,15 @@ func TestLabelParsing(t *testing.T) {
 
 func TestHelmState_applyDefaultsTo(t *testing.T) {
 	type fields struct {
-		BaseChartPath      string
-		Context            string
+		BaseChartPath string
+		Context       string
+
+		// TODO: Remove this function once Helmfile v0.x
 		DeprecatedReleases []ReleaseSpec
-		Namespace          string
-		Repositories       []RepositorySpec
-		Releases           []ReleaseSpec
+
+		Namespace    string
+		Repositories []RepositorySpec
+		Releases     []ReleaseSpec
 	}
 	type args struct {
 		spec ReleaseSpec
@@ -82,11 +85,14 @@ func TestHelmState_applyDefaultsTo(t *testing.T) {
 	specWithNamespaceFromFields.Namespace = "test-namespace-field"
 
 	fieldsWithNamespace := fields{
-		BaseChartPath:      ".",
-		Context:            "test_context",
+		BaseChartPath: ".",
+		Context:       "test_context",
+
+		// TODO: Remove this function once Helmfile v0.x
 		DeprecatedReleases: nil,
-		Namespace:          specWithNamespaceFromFields.Namespace,
-		Repositories:       nil,
+
+		Namespace:    specWithNamespaceFromFields.Namespace,
+		Repositories: nil,
 		Releases: []ReleaseSpec{
 			specWithNamespace,
 		},
@@ -140,11 +146,13 @@ func TestHelmState_applyDefaultsTo(t *testing.T) {
 			state := &HelmState{
 				basePath: tt.fields.BaseChartPath,
 				ReleaseSetSpec: ReleaseSetSpec{
+					// TODO: Remove this function once Helmfile v0.x
 					DeprecatedContext:  tt.fields.Context,
 					DeprecatedReleases: tt.fields.DeprecatedReleases,
-					OverrideNamespace:  tt.fields.Namespace,
-					Repositories:       tt.fields.Repositories,
-					Releases:           tt.fields.Releases,
+
+					OverrideNamespace: tt.fields.Namespace,
+					Repositories:      tt.fields.Repositories,
+					Releases:          tt.fields.Releases,
 				},
 			}
 			if state.ApplyOverrides(&tt.args.spec); !reflect.DeepEqual(tt.args.spec, tt.want) {
@@ -768,9 +776,11 @@ func TestHelmState_flagsForUpgrade(t *testing.T) {
 			state := &HelmState{
 				basePath: "./",
 				ReleaseSetSpec: ReleaseSetSpec{
+					// TODO: Remove this function once Helmfile v0.x
 					DeprecatedContext: "default",
-					Releases:          []ReleaseSpec{*tt.release},
-					HelmDefaults:      tt.defaults,
+
+					Releases:     []ReleaseSpec{*tt.release},
+					HelmDefaults: tt.defaults,
 				},
 				valsRuntime: valsRuntime,
 			}