Odoo, ERPNext or SAP Business One for a mid-size company

Count users, legal entities and warehouses before reading any brochure. A firm with one entity, one warehouse and thirty users has very different needs from a group with five companies and intercompany billing. Put the numbers on one page so every partner quotes against the same facts instead of guessing from a phone call.

Odoo scales down gracefully and lets you start with two apps, such as sales and inventory. ERPNext suits owner-run businesses that want everything in one place and have a team able to tweak forms. SAP Business One expects a clearer process map and a trained partner from day one.

Be honest about internal skills. If nobody on staff can maintain scripts, you will pay a partner for every change.

All three cover sales, purchase, inventory, accounts and basic HR. The trouble sits at the edges. Batch-tracked manufacturing, project billing, subcontracting, landed cost and multi-level approvals behave differently in each product.

Write down five of your hardest real transactions and ask every partner to run them live. A purchase return with a partial credit note makes a good test. So does a stock transfer between two branches with goods still in transit. Watch how many clicks each takes, and whether the partner reaches for a custom script to make the transaction work.

A polished demo on invented data proves little. Insist on your own item master and a sample of your own invoices.

Every custom field and script becomes a future upgrade problem. Odoo’s community edition has open source, but heavy modifications can clash with version jumps. ERPNext’s Frappe framework keeps custom apps tidy, yet they still need testing at every release.

SAP Business One favours add-ons and user-defined fields over changes to core logic. Ask each partner how their last three customers upgraded. How long was the system frozen? Which custom pieces broke?

If a requirement can be met by changing your process, change the process. Customise only where the difference earns you money. A short list of agreed exceptions, signed off by a director, keeps the project from sliding into a bespoke build nobody can upgrade.

The software matters less than the team that configures it. Look for a partner with live customers in your trade, named consultants and a support desk that answers on the day. Ask to speak with two customers who went live more than a year ago. Ask whether the partner will still support your customisations if you move hosting later, because some will not, and the answer shapes the whole bill.

Open products attract many small implementers of uneven quality, whereas SAP keeps a smaller and more formal network. Neither pattern is better. A weak partner on a strong product still produces a poor result.

Check that your contract lets you change partners. Credentials, customisation code and documentation must be yours.

Decide what moves. Masters for customers, vendors, items and the chart of accounts almost always do. Opening balances and open orders usually do. Ten years of old invoices often stay in an archive. Dates matter as well, since open invoices need the same treatment on both sides of the cutover and the cutover day is usually a weekend.

Clean before you move. Duplicate customers, items with three spellings and unmatched vendor ledgers will follow you into the new system and ruin the first month-end. Run two trial migrations into a test copy and reconcile trial balance and stock value against the old books.

Start by exporting your item and party lists to a spreadsheet and counting the duplicates.