ERP automation: what to automate inside the workflow engine and what to run around it

Inside the ERP or around it: where the line goes

Automate inside the ERP's own workflow engine when the process runs on fixed rules within one system, such as approval routes and separation of duties. Automate around the ERP when the work starts with unstructured input, crosses several systems or depends on judging a case the rules did not foresee.

In Business Central, for example, approval requests are typical workflow steps, and automatic posting can be included as a step. A standard supplier invoice that follows a known approval route belongs in that kind of engine. An invoice that deviates, with the explanation sitting in an email or a message from purchasing, is a different kind of case: a rule can route it to someone, but it cannot read why the amount differs.

In the approach this article recommends, an AI agent reads the deviating case and proposes an action, deterministic code checks amounts and rules, and a named person approves before anything changes in the ERP. The ERP stays the system of record; the outside layer handles the cases its rules cannot decide.

If one of your processes already splits this way, reviewing that single process is a practical place to start.

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What Business Central and Fortnox automate on their own, and what to check in Monitor G5

Business Central and Fortnox automate approval routing on rules you configure in advance, and Business Central can also include automatic posting as a workflow step. For Monitor G5, we have not verified what its in-system workflow features cover, so confirm them with your Monitor partner before deciding what to build around it.

Microsoft describes a Business Central workflow as a sequence of tasks triggered by an action, a condition or a rule, typically used for separation of duties and unified processes. Flows that connect to other internal and external sources run through Power Automate and the Business Central connector.

Fortnox lets you apply a supplier invoice approval flow automatically based on the supplier, a reference on the invoice or both. Invoices arriving as e-invoices or via invoice interpretation can go straight to the first approver.

As one example of a connection around Monitor G5, a third-party add-on links machines to the ERP for automatic feedback of worked time, quantities and downtime.

Once you know what your own ERP's engine covers, the exceptions left over show what an outside layer would need to handle.

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Inside the workflow engine vs around the ERP

Worked example (illustrative): a supplier invoice that deviates from its order

1. The ERP routes the standard case

   All numbers in this example are illustrative. A purchase order for 2,000 steel brackets at 4.20 per unit, 8,400 in total, is received in full. The supplier's invoice for 8,400 follows the approval route you have configured for that supplier in the ERP, the cost-centre approver approves it and it is posted. No agent is involved.

2. The exception reaches the approver

   In this example, a second invoice for the same order arrives at 9,100, which is 700 more than the order. The same supplier rule routes it to the same approver, who sees that it does not match the order and does not approve it. In this setup, this is where the ERP's engine stops: its rule decides who sees the invoice, but the explanation for the 700 sits in an email outside the system. The example does not rely on any automatic order matching; if your ERP has one, check how it behaves in your own system.

3. An agent reads the deviating case

   In this hypothetical setup, an agent outside the ERP has read access to the purchasing mailbox. It finds the supplier's email: a raw-material surcharge of 0.35 per unit, agreed with purchasing by phone. It links the email to the order and drafts a proposed action: accept the surcharge as a separate line, with the email attached as the source.

4. Code checks amounts and rules

   In this example, deterministic code, not the language model, recalculates 2,000 × 0.35 = 700, confirms that 8,400 plus 700 equals the invoiced 9,100, and checks the surcharge against rules you set, such as a tolerance or a requirement that purchasing has confirmed it. Here all checks pass; any failed check would stop the proposal.

5. A named approver signs off

   In this example, the proposal goes to the named approver, the purchasing manager, together with the email, the calculation and the check results. The approver accepts, rejects or edits it. Nothing changes in the ERP before this decision.

6. The ERP takes over again

   After approval, the change is entered in the ERP and follows its normal approval and posting route. The ERP stays the system of record. Keep a record of what the agent read, what the code checked and who approved, so the exception can be traced afterwards.

Controls that keep an AI agent safe around an ERP

• The agent drafts, it does not post

  Microsoft's Payables Agent for Business Central reads emailed vendor invoices and shows drafts for review; its review is not an approval workflow, and it does not post the invoice.

• Human approval for high-impact actions

  OWASP advises human-in-the-loop control so that a person approves high-impact actions before they are taken. Which ERP changes count as high-impact is your decision; this article treats postings and order changes as such.

• Authorisation is enforced outside the model

  OWASP recommends implementing authorisation in downstream systems rather than relying on a language model to decide whether an action is allowed.

• Code calculates every amount

  Totals, tolerances and matches come from explicit code, so the same input gives the same result every time.

• New master data starts blocked

  When the Payables Agent creates a vendor, Business Central sets it to Blocked: All so normal vendor approval can take place. Apply the same rule to anything an agent creates.

• Least-privilege access

  Give the agent read access to what it needs to interpret the case, and no standing right to change postings or orders.

• Every step is traceable

  Log what the agent read, what the code checked and who approved. In Sweden, BFN's bookkeeping guidance covers system documentation and processing history, so confirm with your auditor what automated steps must record.

Who this approach suits, and who it does not

How to decide where the line goes for your own processes

Start from the exceptions, not the system. Take one process, such as supplier invoices or customer order changes, and sort its cases into those the ERP's rules already resolve and those that fall out to a person.

Keep a case inside the ERP if a fixed rule could decide it and all the data is in the system, and configure the engine first so the logic stays in the system of record. Move a case outside if it needs input the ERP cannot read, a step in another system, or interpretation. Before building anything, list who approves, which amounts code must check and which permissions the agent needs.

Ronja connects to the systems a company already uses, which stay in place, and builds and runs modules for the work between them. Its principle has three steps: AI interprets ambiguous input, deterministic code calculates and validates, and people approve consequential decisions. For Presso, Ronja has made data from Monitor G5 accessible across production, materials, purchasing, inventory, customer orders and finance.

Pick the one process where exceptions cost the most time and review it with Ronja before building anything.

Talk to us

Review one bounded process with Ronja.

Sources

• Microsoft Learn – Use approval workflows in Business Central
• Microsoft Learn – Use Power Automate flows in Business Central
• Microsoft Learn – Payables Agent overview in Business Central
• OWASP Gen AI Security Project – LLM06:2025 Excessive Agency
• Fortnox – Leverantörsfakturaattest, generella inställningar
• Fortnox – Skapa nytt attestflöde
• Good Solutions – Addon Monitor ERP G5 Standard 2-way integration
• Bokföringsnämnden – Vägledningar
• Ronja – Ronja platform