diff --git a/src/ledger/file.go b/src/ledger/file.go
index f62fd8c..287f7c1 100644
--- a/src/ledger/file.go
+++ b/src/ledger/file.go
@@ -26,7 +26,53 @@ func NewFiles(p string, q ...string) (Files, error) {
 }
 
 func (files Files) Amend(old, now Delta) error {
-	return io.EOF
+	xactions, err := files.transactions()
+	if err != nil {
+		return err
+	}
+	var transaction transaction
+	for _, xaction := range xactions {
+		if xaction.name != old.transaction {
+			continue
+		}
+		transaction = xaction
+		break
+	}
+
+	inverted := transaction.deltas()
+	for i := range inverted {
+		inverted[i].Value *= -1
+	}
+
+	if now.isSet {
+		return fmt.Errorf("cannot ammend: immutable isSet is set")
+	}
+	transaction.date = now.Date
+	transaction.description = now.Description
+	if transaction.payee == old.Name {
+		if len(transaction.recipients) != 1 {
+			return fmt.Errorf("cannot amend: modifying original payee, but many recipients cant share new value")
+		}
+		old.Value *= -1
+		old.Name = transaction.recipients[0].name
+	}
+	idx := -1
+	for i, recipient := range transaction.recipients {
+		if recipient.name == old.Name && recipient.value == old.Value {
+			idx = i
+		}
+	}
+	if idx == -1 {
+		return fmt.Errorf("cannot amend: no recipient with name %s found to set new value", old.Name)
+	}
+	transaction.recipients[idx].name = now.Name
+	transaction.recipients[idx].value = now.Value
+	transaction.recipients[idx].currency = string(now.Currency)
+	amendedDeltas := transaction.deltas().Like(func(d Delta) bool {
+		return d.Name != transaction.payee
+	})
+
+	return files.Add(transaction.payee, append(inverted, amendedDeltas...)...)
 }
 
 func (files Files) TempGetLastNLines(n int) ([]string, error) {
@@ -134,7 +180,16 @@ func (files Files) paths() []string {
 	return result
 }
 
-func (files Files) Add(payee string, delta Delta) error {
+func (files Files) Add(payee string, deltas ...Delta) error {
+	for _, delta := range deltas {
+		if err := files.add(payee, delta); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (files Files) add(payee string, delta Delta) error {
 	currencyValue := fmt.Sprintf("%s%.2f", delta.Currency, delta.Value)
 	if delta.Currency != USD {
 		currencyValue = fmt.Sprintf("%.2f %s", delta.Value, delta.Currency)
@@ -214,39 +269,7 @@ func (files Files) Deltas(like ...Like) (Deltas, error) {
 
 	result := make(Deltas, 0, len(transactions)*2)
 	for _, transaction := range transactions {
-		sums := map[string]float64{}
-		for _, recipient := range transaction.recipients {
-			sums[recipient.currency] += recipient.value
-			delta := newDelta(
-				transaction.name,
-				transaction.date,
-				transaction.description,
-				recipient.name,
-				recipient.value,
-				recipient.currency,
-				recipient.isSet,
-			)
-			result = append(result, delta)
-		}
-		for currency, value := range sums {
-			if value == 0 {
-				continue
-			}
-			if transaction.payee == "" {
-				//return nil, fmt.Errorf("didnt find net zero and no dumping ground payee set: %+v", transaction)
-			} else {
-				delta := newDelta(
-					transaction.name,
-					transaction.date,
-					transaction.description,
-					transaction.payee,
-					-1.0*value,
-					currency,
-					false,
-				)
-				result = append(result, delta)
-			}
-		}
+		result = append(result, transaction.deltas()...)
 	}
 
 	balances := make(Balances)
diff --git a/src/ledger/file_test.go b/src/ledger/file_test.go
index 0ec6d3c..511ad19 100644
--- a/src/ledger/file_test.go
+++ b/src/ledger/file_test.go
@@ -11,12 +11,61 @@ import (
 )
 
 func TestFileAmend(t *testing.T) {
-	// given real xaction
-	// find it
-	// invert it
-	// modify original delta to requested
-	// modify counterpart
-	// inbox.txt has xaction inverted and xaction'
+	cases := map[string]struct {
+		from string
+		old  Delta
+		now  Delta
+		want string
+	}{
+		//"was set payee": {
+		//"payee": {
+		//"recipient": {
+		//"multi recipient": {
+		"was set": {
+			from: `
+            2006-01-02  description
+               recipient  $3.45
+               payee
+         `,
+			old: Delta{
+				Date:        "2006-01-02",
+				Name:        "recipient",
+				Value:       3.45,
+				Currency:    "$",
+				Description: "description",
+			},
+			now: Delta{
+				Date:        "2106-11-12",
+				Name:        "recipient",
+				Value:       3.45,
+				Currency:    "$",
+				Description: "description",
+			},
+		},
+	}
+
+	for name, d := range cases {
+		c := d
+		t.Run(name, func(t *testing.T) {
+			p := path.Join(t.TempDir(), "dat")
+			if err := os.WriteFile(p, bytes.TrimSpace([]byte(c.from)), os.ModePerm); err != nil {
+				t.Fatal(err)
+			}
+
+			files, err := NewFiles(p)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if err := files.Amend(c.old, c.now); err != nil {
+				t.Fatal(err)
+			} else if b, err := os.ReadFile(path.Join(path.Dir(p), "inbox.dat")); err != nil {
+				t.Fatal(err)
+			} else if b := bytes.TrimSpace(b); string(b) != c.want {
+				t.Fatalf("expected \n\t%s\nbut got\n\t%s", c.want, b)
+			}
+		})
+	}
 }
 
 func TestFileAdd(t *testing.T) {
diff --git a/src/ledger/transaction.go b/src/ledger/transaction.go
index ddfbf26..e1a9f2c 100644
--- a/src/ledger/transaction.go
+++ b/src/ledger/transaction.go
@@ -30,6 +30,42 @@ type transactionRecipient struct {
 	isSet    bool
 }
 
+func (t transaction) deltas() Deltas {
+	result := []Delta{}
+	sums := map[string]float64{}
+	for _, recipient := range t.recipients {
+		sums[recipient.currency] += recipient.value
+		result = append(result, newDelta(
+			t.name,
+			t.date,
+			t.description,
+			recipient.name,
+			recipient.value,
+			recipient.currency,
+			recipient.isSet,
+		))
+	}
+	for currency, value := range sums {
+		if value == 0 {
+			continue
+		}
+		if t.payee == "" {
+			//return nil, fmt.Errorf("didnt find net zero and no dumping ground payee set: %+v", transaction)
+		} else {
+			result = append(result, newDelta(
+				t.name,
+				t.date,
+				t.description,
+				t.payee,
+				-1.0*value,
+				currency,
+				false,
+			))
+		}
+	}
+	return result
+}
+
 func (t transactionRecipient) empty() bool {
 	return t == (transactionRecipient{})
 }