Nigerian businesses running Odoo hit a wall the moment FIRS compliance becomes real. Out of the box, Odoo ships a generic tax engine and a country-agnostic chart of accounts, but it has no concept of the FIRS Merchant-Buyer System (MBS) e-invoicing mandate, no built-in 7.5% VAT logic wired to Nigerian tax reporting, and no withholding-tax mechanism that computes and posts WHT on vendor payments the way FIRS expects. Finance teams end up hand-keying VAT returns, tracking WHT credit notes in spreadsheets, and manually formatting invoices to satisfy the electronic-invoicing rules — error-prone work that becomes a real audit and penalty risk as FIRS tightens enforcement across large and medium taxpayers.

ECOSIRE builds a dedicated localization module that closes those gaps inside Odoo rather than bolting a third-party tool onto it. At the data layer we ship a Nigeria-specific chart of accounts and a full tax structure defined as account.tax records — 7.5% VAT (standard, zero-rated and exempt) plus WHT tax groups for the common statutory rates on services, rent, dividends, interest and contracts. TIN validation is added on res.partner via a constrains/onchange layer so malformed or missing taxpayer IDs are caught at data entry, not at return time. The e-invoicing connector is implemented as an Odoo model that serializes each posted account.move into the FIRS-required payload, signs/authenticates against the FIRS API over the JSON-RPC/HTTPS transport, stores the returned IRN and QR/validation reference back on the invoice, and exposes the transmission state (draft → submitted → validated → rejected) as a tracked field so accountants can see exactly where every document stands.

Technically it is a clean Odoo addon. The __manifest__.py declares dependencies on account (and l10n_generic_coa where relevant) and is pinned to your Odoo series. Business logic lives in models/ using models.Model, typed fields, and compute methods decorated with @api.depends so VAT and WHT amounts recalculate deterministically. Access is governed by ir.model.access.csv plus record rules so only accounting roles can transmit or void e-invoices. The UI is delivered as XML views (with OWL components where an interactive submission widget helps), and the statutory outputs — VAT return summary, WHT schedule, and a FIRS-compliant invoice PDF carrying the IRN and QR code — are QWeb reports. An ir.cron automated action can batch-submit the day's validated invoices and retry transient FIRS failures. We build it to work on Odoo Community as well as Enterprise; where a feature depends on an Enterprise-only app we flag it during scoping so there are no surprises.

Because this is build-to-order, nothing is pre-listed on apps.odoo.com and there is no instant download. You start with a short scoping call where we confirm your Odoo version (17.0/18.0/19.0), Community vs Enterprise, which WHT rates and VAT treatments apply to your sector, your FIRS onboarding/API credentials, and any existing chart of accounts we must map to rather than replace. We then build against your requirements, deliver on a staging environment for UAT, and only cut over to production once you sign off. Typical delivery is one working week from confirmed scope, and you receive the full source so you are never locked in.