Allowances and charges

Allowances lower the amount due, charges raise it. At document level they are BG-20 and BG-21 and carry a VAT category; at line level (BG-27, BG-28) they change the line's net amount. The snippets extend the base invoice.

Document level

chargeIndicator is 'false' for an allowance and 'true' for a charge. Give a reason as text, as a code (UNCL5189 for allowances, UNCL7161 for charges), or both. State the amount, or a percentage and the base amount it applies to.

const allowanceCharge: InvoiceInput['allowanceCharge'] = [
  {
    chargeIndicator: 'false', // an allowance
    allowanceChargeReasonCode: '95', // UNCL5189: discount
    allowanceChargeReason: 'Loyalty discount',
    amount: 100,
    taxCategory: { id: 'S', percent: 25 },
  },
  {
    chargeIndicator: 'true', // a charge
    allowanceChargeReasonCode: 'FC', // UNCL7161: freight service
    allowanceChargeReason: 'Freight',
    multiplierFactorNumeric: 2.5, // 2.5 % ...
    baseAmount: 2800, // ... of 2800.00: the builder computes amount = 70.00
    taxCategory: { id: 'S', percent: 25 },
  },
];

Computed: amount from multiplierFactorNumeric and baseAmount when you leave it out.

Line level

A line allowance or charge has no VAT category of its own: it takes the line's.

const [line] = baseInvoice.invoiceLine;
if (line === undefined) {
  throw new Error('baseInvoice has a line');
}

const invoiceLine: InvoiceInput['invoiceLine'] = [
  {
    ...line,
    allowanceCharge: [
      {
        chargeIndicator: 'false',
        allowanceChargeReasonCode: '95',
        allowanceChargeReason: 'Volume discount',
        amount: 300,
      },
    ],
  },
];
// lineExtensionAmount: 7 × 400.00 − 300.00 = 2500.00

Computed: the line's lineExtensionAmount includes them.

Effect on the totals

const invoice = createInvoice({ ...baseInvoice, allowanceCharge, invoiceLine });

const totals = invoice.legalMonetaryTotal;
// lineExtensionAmount   2500.00  Σ line net amounts (BT-106)
// allowanceTotalAmount   100.00  Σ document allowances (BT-107)
// chargeTotalAmount       70.00  Σ document charges (BT-108)
// taxExclusiveAmount    2470.00  2500.00 − 100.00 + 70.00 (BT-109)
// taxInclusiveAmount    3087.50  plus 25 % VAT on 2470.00 (BT-112)
// payableAmount         3087.50  (BT-115)

Computed: every total above, and the VAT breakdown, where each document level allowance or charge counts in its VAT category.