The accounting model

Numina is a double-entry ledger for Danish companies. Every transaction is a set of lines on accounts that sum to zero. The API exposes that model directly, so it pays to know four rules before you write.

Signs

Amounts are signed: positive is debit, negative is credit.

The same convention holds in responses: on a revenue account, the balance endpoints return negative totals.

Balanced lines

A journal entry has at least two lines, and their amounts sum to exactly zero in DKK. An unbalanced entry fails with 400 validation_error.

{
  "lines": [
    { "account_number": 2450, "amount": 500, "vat_code": "I25" },
    { "account_number": 6480, "amount": -500 }
  ]
}

Lines refer to accounts by number. Numbers differ between companies, so read them from List accounts rather than hard-coding them.

VAT

Put the VAT code on the line it applies to, and Numina splits out the VAT when the entry is booked.

• Danish VAT codes (I25 for deductible purchase VAT, U25 for sales VAT) take the gross amount, VAT included. The 500 DKK line above becomes 400 DKK of expense and 100 DKK of VAT.
• Reverse-charge codes take the net amount; Numina adds both VAT lines.

List VAT codes returns the codes a company uses, with their rates and types.

Drafts and booking

What an integration creates starts as a draft. It changes the books only when it is booked.

1. Draft

   A journal entry from the API arrives in Numina’s journal with status open. Drafts do not affect balances and can still be changed or deleted, so treat their figures as provisional.

2. Booked

   Booking splits out VAT, writes the final ledger entries and locks them. A booked entry is final: it is corrected in Numina with reversing entries.

A person can book a draft in Numina, or your integration can book it with Book journal entry and the journal:book scope. The entry needs a document first. Invoices work the same way with invoices:book: Book draft invoice, or book: true when you create one. Booking assigns the invoice number but does not send it.

Currency and dates

• DKK is the base currency. Ledger amounts and balances are DKK; invoices carry their own currency and a currency_rate to DKK.
• Dates are YYYY-MM-DD with no time zone. A company’s accounting years decide which periods balance-sheet reports can span.