Automation for accounting firms that know their tech stack is holding them back
Multi-office practices, post-acquisition integrations, finance teams running on five different tools. We've seen it. We can help — without selling you yet another platform.
Your stack grew by acquisition. Now it's paying the cost.
Accountancy and practice management firms over 100 staff almost always end up here: Xero for one tranche of clients, Sage for another, QuickBooks for the ecommerce crowd. Karbon or Senta for practice management. Microsoft 365 and SharePoint for everything else. Each tool works — but the gaps between them are where the hours and errors live.
- Multi-ledger client bases — Consolidated reporting across Xero, Sage and QuickBooks portfolios without forcing clients to migrate.
- Practice management gaps — Karbon, Senta, AccountancyManager, BrightManager — all solve part of the problem. None cover the edges without configuration.
- Microsoft-centric ops — SharePoint, Teams, Power Automate, Excel. We work inside what you already have — we don't rip and replace.
The honest answer is usually "configure what you own"
The accountancy software market is loud. Every vendor has a practice management suite, an AI assistant, or a "platform that unifies your stack." Most of what they promise, you already own — it's just not configured. Before we build or buy anything, we audit what's already sitting unused in your tenant.
- Buy — When a category-leading tool is cheaper than the total cost of building. We'll name the ones we trust — Karbon for practice management, FYI for documents, Dext for capture.
- Build — When you have unique workflows no off-the-shelf tool fits. Usually post-acquisition consolidation, bespoke client reporting, or internal AI assistants.
- Configure — The answer 60% of the time. Power Automate, SharePoint lists, Xero workflows and Karbon automations, set up properly by someone who knows the craft.
Automations that actually move a practice's numbers
Patterns we've implemented repeatedly across UK accountancy firms. Every one of these starts with a flat-fee discovery so you know the ROI before you commit.
Four phases, flat fee, no retainer
Built for firms that have been burned by retainer-heavy consultancies and want a clearer commercial structure.
We interview partners, operators and client-facing staff. We audit your existing stack — Microsoft 365, Xero/Sage/QuickBooks, Karbon/Senta, any custom tooling. Output: a map of where time and margin are leaking.
For each opportunity: estimated hours saved, error reduction, payback period. Explicit build/buy/configure recommendation. You pick which to run.
We build or configure alongside your team. Your operators learn the stack as it goes live. Documentation as we go — not a 200-page handover at the end.
Your team runs it. We're on call for 90 days at no extra charge. After that, we step back unless you want us to scope the next project.
Why UK accounting firms are hiring automation consultants
The UK accountancy market is in the middle of a consolidation wave. Private equity-backed roll-ups, mid-tier firms acquiring smaller practices, and succession-driven mergers have created a new class of 100-to-500-person practice that didn't exist five years ago. Those firms have inherited, variously: two or three ledger systems, multiple practice management tools, overlapping CRM and document management platforms, and a team structure that's part legacy, part acquired. The automation opportunity is enormous. It's also terrifying to execute.
The wrong response is to buy "the platform that unifies everything." There isn't one — and the firms marketing themselves that way are usually reselling a Microsoft Power Platform deployment you could have done in-house. The right response is a disciplined audit of what you already own, honest advice on where the gaps are, and targeted builds for the handful of workflows that actually drive margin.
Common automation patterns we see in accounting firms
There's a shortlist of workflows where we consistently see strong ROI for practices over 50 staff:
- Client onboarding. The process from new-business enquiry to first invoice typically touches 6–10 tools. Automating the handoffs saves around 40 minutes per client and removes the main source of onboarding dropouts ("we never got the engagement letter signed").
- Document capture and filing. Inbound client documents arrive by email, portal, post and Dext. Classifying, renaming, routing and logging them against jobs is a meaningful tax on fee earners. Modern OCR + LLM classification handles 80–90% accurately with human review for the rest.
- Deadline and workflow management. Most practice management tools do this — badly, or well for one type of work. Layering a custom orchestration on top that understands VAT, PAYE, year-end and corporation tax simultaneously is frequently the highest-ROI build.
- Portfolio-level reporting. Partners want live client-level KPIs without waiting for month-end reports. Building a read-only aggregation over Xero/Sage/QuickBooks into a Power BI or Lightdash dashboard is cheap, low-risk and dramatically changes how partners manage the book.
- Internal AI assistants. An LLM trained on your firm's technical manuals, tax bulletins and engagement playbooks is a cheap and genuinely useful tool — particularly for junior staff. It's also, increasingly, table stakes for recruitment.
The build-vs-buy question
The biggest commercial decision most mid-sized practices face right now is: do we buy a category-leading SaaS tool (Karbon, FYI, Silverfin), do we extend what we already have in Microsoft 365, or do we commission a custom build?
There's no universal answer. But there's a decision framework that helps:
- If the workflow is shared by every accounting firm in your peer set (timesheet capture, email filing, invoice raising), buy the category leader. The vendors have solved it better than you will.
- If the workflow is specific to your practice's structure or client mix (bespoke consolidation logic, multi-ledger client reporting, unique approvals), configure inside Microsoft 365 or build in a lightweight platform like Xano.
- If the workflow is shared across firms but poorly solved by the market (cross-system practice dashboards, multi-jurisdiction deadline tracking), a custom build is often cheaper and better than the SaaS alternative.
This is the decision we help with most often. We don't resell any of the category-leading tools — we're genuinely indifferent to which you pick, which makes the advice trustworthy.
What to expect from an engagement
A typical practice engagement with Watermelon runs 8–14 weeks end-to-end. Discovery and strategy are priced together at a flat fee (usually £8k–£15k depending on firm size). Implementation is priced per project, scoped from the strategy phase, with no open-ended billing. We take on one firm at a time in each discovery phase so our attention isn't diluted.
After the 90-day handover, we step back unless you commission another project. We don't run managed services for accounting firms. If your team can't own the stack, we haven't done our job.
Related
- Automation Consulting — the broader service, if you're still scoping whether automation is the right answer.
- AI Automation Agency — specifically for AI-led workflows and agent-based systems.
- Business Process Automation — for post-acquisition consolidation and operational standardisation.
Ready to talk?
Bring one workflow that's costing you partner hours. 30 minutes, no pitch. We'll tell you how we'd approach it.
In the words of the people who hired us
"We'd been looking at six-figure migrations for two years. Watermelon ran a two-week audit and showed us how to get 90% of the value by properly configuring Karbon and Power Automate. The remaining 10% got built in three months. We've saved more than the entire consultancy fee in year one."
"The honest build-vs-buy advice alone was worth the engagement. They told us not to buy two of the platforms we'd been evaluating. No consultancy had done that for us before."
"The practice dashboard pulling live data from our three ledger systems changed how our partners manage the book. It was quoted at £120k by another firm. Watermelon built it for £22k and handed it over in 9 weeks."
One workflow. 30 minutes. Honest advice.
Tell us the workflow in your practice that's costing the most partner time. We'll tell you whether it's worth automating, what we'd build, and what it would cost. No pitch deck.