For Business Central to be usable in Turkey, a localisation package is mandatory. That package comes not from Microsoft but from certified partners, and is installed via AppSource.
01. Package Scope
A standard localisation package brings: VAT and withholding structures, statutory ledger outputs, period-close functions, currency revaluation, cheque and note tracking, and the e-document modules.
02. e-Document Flow
An invoice issued inside BC goes through the localisation layer to the private integrator. The integrator forwards it to the tax authority, and the returned status code is written back to BC. The invoice can be tracked in BC as sent, accepted or rejected.
03. Which Integrators
Packages generally support more than one integrator. Uyumsoft, İzibiz, EDM and Digital Planet are common options. Before selecting, ask which integrator the partner has already written a connector for; if there isn't one, that means extra development.
04. The e-Ledger Side
e-Ledger concerns accounting more than invoicing. BC's journal entries are converted into a certificate file and uploaded monthly. Mapping the chart of accounts to the tax authority standard is a precondition.
05. Upgrade Risk
Cloud BC receives two major releases a year. If the compatible update to the localisation package doesn't arrive on time, the upgrade is held back. The partner's update commitment should be written into the contract.