The difference between accounts payable software and an AP managed service is who runs it. With software, your firm buys a tool and your own people configure it, maintain its rules, work its exception queue and keep it current. With a managed service, a provider operates the process for you inside limits you set, while your firm keeps ownership of the ledger, the authority and the accountability. The right choice depends less on features than on whether you have the people and the time to run another system.
Software is a licence and a set of capabilities. It arrives configured to a sensible default and becomes useful once someone in your team has mapped suppliers, set coding rules, connected the ledger and decided who approves what. After that, someone has to keep it that way: new suppliers, changed cost centres, a reorganised chart of accounts, a vendor upgrade that moves a setting you relied on.
A managed service is an operated outcome. The provider does the mapping, the rule maintenance and the day-to-day running. You receive processed invoices, a queue of genuine exceptions and a record of what was done. You still decide the rules. You no longer administer them.
A useful way to compare the two is to list the recurring work and ask who does each item:
That last line is the one that matters.
A managed service does not transfer accountability for your books. Directors remain responsible for the company's accounting records whoever operates the process. So whichever route you choose, insist that three things stay with you: the signed authority that defines what may be posted without a person, a named individual in your firm who owns the posting decision, and a complete record of every decision that you can take with you if you leave.
If a provider is vague about any of those, the arrangement is outsourcing in the old sense, and you will rediscover the problem at audit.
Software suits a firm that already has an AP function with spare capacity, someone comfortable administering systems, a stable supplier base and a preference for owning the configuration. It fits finance teams that want control over every setting and have the people to exercise it.
A managed service fits when transaction volume has outgrown a lean finance team, when nobody has time to administer another tool, and when the finance owner wants an outcome rather than a project. That describes many independent services firms: an MSP with a two-person finance function and hundreds of supplier invoices a month, or an agency whose financial controller also runs payroll and the management accounts.
AI has made the managed service model more practical, because a provider can operate the routine decisions at volume and route only the unclear ones to people. It has also raised the governance stakes. Databricks, in its State of AI Agents 2026 report, finds that companies that actively govern AI put 12 times more projects into production. The same report cites MIT Technology Review research showing that 19% of organisations have deployed AI agents. Adoption is early, and governance is what separates the projects that run from the ones that stall.
For a managed service using AI, that means asking the same questions you would ask of software, and then some: what the system may decide on its own, how confident it was, who it escalated to, and where the record lives.
Clear, written answers to these are worth more than any feature comparison.
Mandate runs accounts payable as a managed service. Its agent, Invoice Maestro, makes the posting decision on supplier invoices inside a mandate your finance owner signs, scores its confidence on five factors, escalates unclear cases to a named person in your firm, and writes every decision to a tamper-evident, append-only audit trail. It works with Xero and Microsoft Dynamics 365 Business Central and is UK-hosted (AWS London, eu-west-2). The way to judge whether a managed service suits you is the 60-Day Proof: sixty days on your own invoices, read-only and free, across two month-ends, with a day-60 report you keep and a rolling monthly contract from day 61 only if you choose. See runmandate.co.uk/60-day-proof.
It is similar in that someone else runs the process, and different in what you should keep. A well-designed service leaves authority, accountability and the full decision record with your firm.
Yes, if the rules and the decision record are documented and exportable. Ask for that commitment before you start, not when you leave.
It should not need payment authority to process and post supplier invoices. Keep payment release a separate, human-controlled step unless you have deliberately decided otherwise.