Use credit-note instead of corrective invoices

Poland doesn't have a distinction between credit notes and
corrective invoices. Our implementation of invoice correction
is closer to what we see in credit notes in other countries.
For example we have differential values for line items.

corrected.go

@@ -5,7 +5,7 @@ import (
 	"github.com/invopop/gobl/head"
 )
 
-// CorrectedInv defines the XML structure for KSeF correction invoiceą
+// CorrectedInv defines the XML structure for KSeF correction invoice
 type CorrectedInv struct {
 	IssueDate           string `xml:"DataWystFaKorygowanej,omitempty"`
 	SequentialNumber    string `xml:"NrFaKorygowanej,omitempty"`
@@ -14,6 +14,7 @@ type CorrectedInv struct {
 	KsefNumber          string `xml:"NrKSeFFaKorygowanej,omitempty"`
 }
 
+// NewCorrectedInv gets credit note data from GOBL invoice
 func NewCorrectedInv(prc *bill.Preceding) *CorrectedInv {
 	inv := &CorrectedInv{
 		SequentialNumber: invoiceNumber(prc.Series, prc.Code),

invoice.go

@@ -95,8 +95,8 @@ func NewInv(inv *bill.Invoice) *Inv {
 		for _, prc := range inv.Preceding {
 			Inv.CorrectedInv = NewCorrectedInv(prc)
 			Inv.CorrectionReason = prc.Reason
-			if prc.Ext.Has(pl.ExtKeyKSEFCorrection) {
-				Inv.CorrectionType = prc.Ext[pl.ExtKeyKSEFCorrection].Code().String()
+			if prc.Ext.Has(pl.ExtKeyKSeFEffectiveDate) {
+				Inv.CorrectionType = prc.Ext[pl.ExtKeyKSeFEffectiveDate].Code().String()
 			}
 		}
 	}

invoice_test.go

@@ -70,7 +70,7 @@ func TestNewInv(t *testing.T) {
 			Preceding: []*bill.Preceding{
 				{
 					Ext: tax.Extensions{
-						pl.ExtKeyKSEFCorrection: "1",
+						pl.ExtKeyKSeFEffectiveDate: "1",
 					},
 				},
 			},

ksef_test.go

@@ -37,14 +37,14 @@ func TestNewDocument(t *testing.T) {
 		assert.Equal(t, output, data)
 	})
 
-	t.Run("should return bytes of the corrective invoice", func(t *testing.T) {
-		doc, err := test.NewDocumentFrom("corrective-invoice.json")
+	t.Run("should return bytes of the credit-note invoice", func(t *testing.T) {
+		doc, err := test.NewDocumentFrom("credit-note.json")
 		require.NoError(t, err)
 
 		data, err := doc.Bytes()
 		require.NoError(t, err)
 
-		output, err := test.LoadOutputFile("corrective-invoice.xml")
+		output, err := test.LoadOutputFile("credit-note.xml")
 		require.NoError(t, err)
 
 		assert.Equal(t, output, data)
@@ -72,7 +72,7 @@ func TestNewDocument(t *testing.T) {
 		assert.Nil(t, validation)
 	})
 
-	t.Run("should generate valid correction invoice", func(t *testing.T) {
+	t.Run("should generate valid credit-note", func(t *testing.T) {
 		err := xsdvalidate.Init()
 		require.NoError(t, err)
 		defer xsdvalidate.Cleanup()
@@ -84,7 +84,7 @@ func TestNewDocument(t *testing.T) {
 		require.NoError(t, err)
 		defer xsdhandler.Free()
 
-		doc, err := test.NewDocumentFrom("corrective-invoice.json")
+		doc, err := test.NewDocumentFrom("credit-note.json")
 		require.NoError(t, err)
 
 		data, err := doc.Bytes()

lines.go

@@ -27,24 +27,13 @@ func newLine(line *bill.Line) *Line {
 		Measure:       string(line.Item.Unit.UNECE()),
 		NetUnitPrice:  line.Item.Price.String(),
 		Quantity:      line.Quantity.String(),
-		UnitDiscount:  unitDiscount(line),
 		NetPriceTotal: line.Total.String(),
 		TaxRate:       line.Taxes[0].Percent.Rescale(2).StringWithoutSymbol(),
 	}
 
 	return Line
 }
 
-func unitDiscount(line *bill.Line) string {
-	if line.Total == line.Sum {
-		return ""
-	}
-
-	discount := line.Total.Subtract(line.Sum).Divide(line.Quantity) // not sure if there should be some rescale or matchPrecision
-
-	return discount.String()
-}
-
 // NewLines generates lines for the KSeF invoice
 func NewLines(lines []*bill.Line) []*Line {
 	var Lines []*Line

payments.go

@@ -6,7 +6,6 @@ import (
 	"github.com/invopop/gobl/bill"
 	"github.com/invopop/gobl/cbc"
 	"github.com/invopop/gobl/regimes/pl"
-	"github.com/invopop/gobl/tax"
 )
 
 // AdvancePayment defines the XML structure for KSeF advance payments
@@ -126,7 +125,7 @@ func findPaymentMeansCode(key cbc.Key) (string, error) {
 	return code.String(), nil
 }
 
-func findPaymentKeyDefinition(key cbc.Key) *tax.KeyDefinition {
+func findPaymentKeyDefinition(key cbc.Key) *cbc.KeyDefinition {
 	for _, keyDef := range regime.PaymentMeansKeys {
 		if key == keyDef.Key {
 			return keyDef

regime.go

@@ -5,4 +5,4 @@ import (
 	"github.com/invopop/gobl/tax"
 )
 
-var regime = tax.RegimeFor(l10n.PL, l10n.CodeEmpty)
+var regime = tax.RegimeFor(l10n.PL)

test/data/credit-note.json

@@ -0,0 +1,120 @@
+{
+	"$schema": "https://gobl.org/draft-0/envelope",
+	"head": {
+		"uuid": "8a51fd30-2a27-11ee-be56-0242ac120002",
+		"dig": {
+			"alg": "sha256",
+			"val": "2dfc5c1c3b11a69e10ba47256e5a1655f5c6dfca99ad6b0390a987588020bbb2"
+		},
+		"draft": true
+	},
+	"doc": {
+		"$schema": "https://gobl.org/draft-0/bill/invoice",
+		"type": "credit-note",
+		"series": "CN",
+		"code": "002",
+		"issue_date": "2023-12-21",
+		"currency": "PLN",
+		"preceding": [
+			{
+				"type": "standard",
+				"series": "SAMPLE",
+				"code": "001",
+				"issue_date": "2023-12-20",
+				"reason": "Special Discount",
+				"stamps": [
+					{
+						"prv": "ksef-id",
+						"val": "9876543210-20231220-107FDF72DB53-F7"
+					}
+				],
+				"ext": {
+					"pl-ksef-effective-date": "2"
+				}
+			}
+		],
+		"supplier": {
+			"name": "Provide One S.L.",
+			"tax_id": {
+				"country": "PL",
+				"code": "9876543210"
+			},
+			"addresses": [
+				{
+					"num": "42",
+					"street": "Calle Pradillo",
+					"locality": "Madrid",
+					"region": "Madrid",
+					"code": "00-015",
+					"country": "PL"
+				}
+			],
+			"emails": [
+				{
+					"addr": "[email protected]"
+				}
+			]
+		},
+		"customer": {
+			"name": "Sample Consumer",
+			"tax_id": {
+				"country": "PL",
+				"code": "1234567788"
+			},
+			"addresses": [
+				{
+					"num": "43",
+					"street": "Calle Pradillo",
+					"locality": "Madrid",
+					"region": "Madrid",
+					"code": "00-015",
+					"country": "PL"
+				}
+			]
+		},
+		"lines": [
+			{
+				"i": 1,
+				"quantity": "20",
+				"item": {
+					"name": "Development services",
+					"price": "10.00",
+					"unit": "h"
+				},
+				"sum": "200.00",
+				"taxes": [
+					{
+						"cat": "VAT",
+						"rate": "standard",
+						"percent": "23.0%"
+					}
+				],
+				"total": "200.00"
+			}
+		],
+		"totals": {
+			"sum": "200.00",
+			"total": "200.00",
+			"taxes": {
+				"categories": [
+					{
+						"code": "VAT",
+						"rates": [
+							{
+								"key": "standard",
+								"base": "200.00",
+								"percent": "23.0%",
+								"amount": "46.00"
+							}
+						],
+						"amount": "46.00"
+					}
+				],
+				"sum": "46.00"
+			},
+			"tax": "46.00",
+			"total_with_tax": "246.00",
+			"payable": "246.00"
+		}
+	}
+}

test/data/out/corrective-invoice.xml → test/data/out/credit-note.xml

@@ -34,10 +34,10 @@
   <Fa>
     <KodWaluty>PLN</KodWaluty>
     <P_1>2023-12-21</P_1>
-    <P_2>COR-002</P_2>
-    <P_13_1>-200.00</P_13_1>
-    <P_14_1>-46.00</P_14_1>
-    <P_15>-246.00</P_15>
+    <P_2>CN-002</P_2>
+    <P_13_1>200.00</P_13_1>
+    <P_14_1>46.00</P_14_1>
+    <P_15>246.00</P_15>
     <Adnotacje>
       <P_16>2</P_16>
       <P_17>2</P_17>
@@ -68,8 +68,8 @@
       <P_7>Development services</P_7>
       <P_8A>HUR</P_8A>
       <P_8B>20</P_8B>
-      <P_9A>-10.00</P_9A>
-      <P_11>-200.00</P_11>
+      <P_9A>10.00</P_9A>
+      <P_11>200.00</P_11>
       <P_12>23</P_12>
     </FaWiersz>
   </Fa>