Saigon Car Care — multi-branch workshop ERP

One system for the whole chain: from the first quotation to the payslip of the technician who did the work.

Client
Saigon Car Care — car care, maintenance and detailing, two branches

Platform
Odoo 17 Community, PostgreSQL, OWL

Scope
Sales, inventory, invoicing, expenses, purchasing, HR & payroll, management reporting, website

Custom modules
Workshop core · Expense & purchasing · HR & payroll

Footprint
17 new models, 11 standard models extended, ~3,400 lines of Python

My role
Systems Analyst & lead implementer — requirements, solution design, module development, data migration, UAT, training

The challenge

The chain ran on an Odoo Enterprise trial that had expired. Quotations, work orders and receipts were printed from ad-hoc templates; service history was tied to customers rather than vehicles, so it was lost whenever a car changed hands; expenses were recorded outside the books; and salary advances and payroll for technicians were calculated by hand in spreadsheets.

The solution

Rather than bolt on generic apps, I designed three tightly integrated modules on top of standard Sales, Inventory and Accounting — each enforcing the business rules the owners had signed off.

Module 1 · Workshop core

Sales, vehicles & documents

Licence-plate-first vehicle registry. Plates are normalised and unique; typing a plate on an order suggests the owner, and an unknown plate creates the vehicle on save.
Ownership history. When a car is sold or traded in, ownership is transferred with a dated history record — the vehicle keeps its full service record while past orders stay with the previous owner.
End-to-end flow: quotation → confirmation → work order → invoice → receipt, with line- and order-level discounts recalculated on untaxed amounts.
Stock-aware ordering. Live availability on each line, an out-of-stock warning before confirmation, automatic delivery validation on invoicing, and an optional warehouse-approval step.
Safe cancellation. Cancelling a delivered, invoiced order generates the stock returns, unreconciles and removes only the payments tied exclusively to that invoice, then cancels the order — no orphaned entries.
Branded print-outs for quotations, work orders, invoices and receipts, with mixed VAT (0% / 8% / 10%) or single-rate layouts, printed straight from the browser or downloaded as PDF.

Module 2 · Expense & purchasing

Every cost on the books

Expense categories mapped to GL accounts (utilities, rent, salaries, advances, purchases…); payment vouchers post directly to the right expense account.
Voucher control: supplier invoice number, due date and a searchable Unpaid / Paid / Overdue status; posted amounts and accounts are locked, only descriptions can change.
Purchase receipts without the Purchase app. One document receives the goods (validated stock move, average cost in the product's base unit) and creates the matching payment; cancelling it checks stock and posts the return.
Revenue vs. expense report — a custom OWL screen aggregating journal items by day, week, month, quarter or year; revenue by account, expenses by category; click any figure to drill into the source entries; export to Excel.

Module 3 · HR & payroll

Advances and payroll without spreadsheets

Salary configuration with monthly history per employee; a configuration locks once it has been used in an approved payroll.
Allowance types paid either as a fixed monthly amount or pro-rata per day worked.
Salary advances with instalment schedules. An advance is repaid over several months; if a month is already closed, the schedule shifts forward automatically and the change is logged. Early repayment is handled by a refund wizard that issues a receipt.
Monthly payroll run: load salaries and planned advance deductions in one click, record leave days, bonuses and penalties; approval is blocked if leave exceeds standard days or net pay would go negative.
Accounting integration. Paying an advance or a payroll creates a payment voucher posted to the salary / advance expense category; un-approving reverses it cleanly.

Delivery

Migrated each branch's live orders, invoices and payments from the Enterprise database, preserving document numbers and reconciliations.
Designed role-based access groups — Sales, Warehouse, Accounting, Marketing, Admin — so each person sees only their own work.
Built a management dashboard (revenue, receivables, uninvoiced orders, new customers, top services) and replicated it across both branches.
Wrote role-based user guides and trained staff on desktop and on the Odoo mobile app.

Outcome

Both branches now run on the same process design: a vehicle's full history is one search away, every document prints in the house format, every cost lands in the right account, and payroll that used to take a day of spreadsheet work is a reviewed, one-click run.

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