How to document a purchase in Guatemala from a vendor who does not issue invoices. The setup and the fields every document shares are in [GT] Electronic Documents (FEL): Overview.

FESP · Factura Especial

document_type: "purchase invoice", invoice_type: "purchase"

Issued by you when you buy from a vendor who does not issue invoices, and you withhold ISR and IVA on that purchase.

supplier_company_id is your company: the one buying.
buyer is the vendor you buy from. Send their CUI (type: "CUI") or NIT (type: "NIT"). A vendor without CUI or NIT, or a person without them, is rejected: a FESP can never be issued to Consumidor Final.

Withholdings

On each item, send the IVA and the withholdings as taxes. Withholdings go with withholding_type: "withholding" and adds_to_final_amount: false:

`name`	`type`	`rate`	`withholding_type`	`adds_to_final_amount`	`amount`
`IVA`	`VAT`	`0.12`	(none)	`true`	IVA of the line
`ISR`	`GIT`	`0.05`	`withholding`	`false`	Required. 5% of the taxable amount
`IVA`	`VAT`	`0.12`	`withholding`	`false`	Equal to the IVA of the line

All of them go with rate_type: "percentage". On the withholdings, taxable_amount (the line amount minus discount) is optional.
With adds_to_final_amount: false, withholdings do not add to final_amount. The net amount you pay is final_amount minus the withholdings.
SAT recalculates the withholdings and rejects the FESP if they differ by more than 0.01.

Payload example

{
  "supplier_company_id": "{{company_id}}",
  "invoice_type": "purchase",
  "document_type": "purchase invoice",
  "invoice_date": "2026-10-27",
  "invoice_external_id": "FESP-4001",
  "currency": "GTQ",
  "e_invoice": true,
  "buyer": {
    "company": {
      "legal_name": "Juan Pérez López",
      "type": "business",
      "address": { "address_line_1": "Aldea El Rosario", "city": "Chimaltenango", "postal_code": "04001", "state": "GT-04", "country": "GT" },
      "tax_registrations": [ { "type": "NIT", "number": "12345678", "level": "country", "location": "GT" } ]
    }
  },
  "items": [
    {
      "name": "Compra de café en grano",
      "quantity": 1,
      "unit_amount": 1000.00,
      "amount": 1000.00,
      "categories": [ { "list": "type", "code": "goods" }, { "list": "unit", "code": "UNI" } ],
      "taxes": [
        { "name": "IVA", "type": "VAT", "rate": 0.12, "rate_type": "percentage", "amount": 120.00, "adds_to_final_amount": true },
        { "name": "ISR", "type": "GIT", "rate": 0.05, "rate_type": "percentage", "taxable_amount": 1000.00, "amount": 50.00, "withholding_type": "withholding", "adds_to_final_amount": false },
        { "name": "IVA", "type": "VAT", "rate": 0.12, "rate_type": "percentage", "taxable_amount": 1000.00, "amount": 120.00, "withholding_type": "withholding", "adds_to_final_amount": false }
      ]
    }
  ]
}

In this example final_amount is Q1,120.00, withholdings are Q170.00 (ISR Q50.00 and IVA Q120.00) and the net amount is Q950.00.