Map Provet Cloud invoices and payments to an ERP system's chart of accounts and financial periods

Steps

1. Build the ERP-facing document number as invoice_prefix + "-" + invoice_number, falling back to the internal id for draft invoices where invoice_number is still null
2. Use the invoice's payer_* snapshot fields (payer_name, payer_vat_number, payer_country_code, etc.) as the authoritative billing address, since they don't change if the client record is edited later
3. Fetch invoice rows via GET /api/0.1/invoicerow/?invoice__is=<id> and map account_number to your revenue GL account; add &expose_invoicerow_vat_group to also get the VAT liability account
4. Before posting a backdated invoice, payment, or credit note, check financial_period_lock_date on GET /api/0.1/settings/department/<id>/ to avoid a validation error
5. Reconcile unallocated payments (prepayments) via modified__gte delta polling, writing your ERP document id back to external_info.external_id to mark records as processed
6. Respect Provet's documented per-endpoint rate limits (e.g. invoice list ~60 req/min) and read the Retry-After header on 429 responses rather than polling at a fixed interval