diff --git a/src/ana/normalize.go b/src/ana/normalize.go
new file mode 100644
index 0000000..256ff9e
--- /dev/null
+++ b/src/ana/normalize.go
@@ -0,0 +1,63 @@
+package ana
+
+import (
+	"regexp"
+	"slices"
+	"strings"
+
+	"gogs.inhome.blapointe.com/ana-ledger/src/ledger"
+)
+
+type Normalizer struct {
+	m map[string][]normalize
+}
+
+type normalize struct {
+	startDate string
+	factor    float64
+}
+
+func NewNormalizer() Normalizer {
+	return Normalizer{
+		m: make(map[string][]normalize),
+	}
+}
+
+func (n Normalizer) With(pattern, startDate string, factor float64) Normalizer {
+	n.m[pattern] = append(n.m[pattern], normalize{startDate: startDate, factor: factor})
+	slices.SortFunc(n.m[pattern], func(a, b normalize) int {
+		return -1 * strings.Compare(a.startDate, b.startDate)
+	})
+	return n
+}
+
+func (n Normalizer) Normalize(deltas ledger.Deltas) ledger.Deltas {
+	deltas = slices.Clone(deltas)
+
+	patterns := []string{}
+	for pattern := range n.m {
+		patterns = append(patterns, pattern)
+	}
+	like := ledger.LikeName(strings.Join(patterns, "|"))
+
+	for i, delta := range deltas {
+		if !like(delta) {
+			continue
+		}
+		func() {
+			for pattern := range n.m {
+				if regexp.MustCompile(pattern).MatchString(delta.Name) {
+					for _, normalize := range n.m[pattern] {
+						if normalize.startDate < delta.Date {
+							delta.Value /= normalize.factor
+							return
+						}
+					}
+				}
+			}
+		}()
+		deltas[i] = delta
+	}
+
+	return deltas
+}
diff --git a/src/ana/normalize_test.go b/src/ana/normalize_test.go
new file mode 100644
index 0000000..bd6a771
--- /dev/null
+++ b/src/ana/normalize_test.go
@@ -0,0 +1,30 @@
+package ana
+
+import (
+	"testing"
+
+	"gogs.inhome.blapointe.com/ana-ledger/src/ledger"
+)
+
+func TestNormalize(t *testing.T) {
+	deltas := ledger.Deltas{
+		ledger.Delta{Date: "2024-12-04", Value: 100, Name: "Bel:Withdrawal"},
+		ledger.Delta{Date: "2024-12-06", Value: 100, Name: "Bel:Withdrawal"},
+	}
+
+	normalizer := NewNormalizer().
+		With("^Bel:", "2024-12-05", 190_000).
+		With("^Bel:", "2018-02-16", 86_000)
+
+	normalized := normalizer.Normalize(deltas)
+	for i, delta := range normalized {
+		t.Logf("[%d] %+v", i, delta)
+	}
+
+	if normalized[0].Value != 100/float64(86_000) {
+		t.Errorf("earliest transaction didnt use earliest salary")
+	}
+	if normalized[1].Value != 100/float64(190_000) {
+		t.Errorf("latest transaction didnt use latest salary")
+	}
+}