Your London ERP stops where the agency P&L meets the FCA-regulated entity
Custom ERP (Enterprise Resource Planning) development in London typically runs £90k to £260k over 5 to 9 months. You build custom when a packaged ERP can't model a Square Mile group with regulated and unregulated entities, multi-currency client billing, and a creative-agency revenue cycle in one ledger. Most London finance teams don't need to replace NetSuite or SAP wholesale; they need a custom layer that makes the consolidation and the FCA-reportable entity stop fighting the agency P&L.
You bought NetSuite or SAP to be the single source of truth, and instead your London group close takes eleven working days because the regulated fintech entity, the media-buying agency, and the EU subsidiary each post differently and nobody trusts the intercompany eliminations. Microsoft Dynamics handled the GL fine until media rebates, deferred agency retainers, and FX on dollar-denominated SaaS contracts turned every period-end into a spreadsheet rescue mission.
Odoo looked affordable for a 60-person Shoreditch firm, but the moment you needed project-level profitability across time-tracked client work, recoverable disbursements, and VAT on cross-border digital services, the off-the-shelf chart of accounts started bending in ways your auditor flagged. The tools aren't broken. They were built for a manufacturer with a warehouse, not a London services group billing time and reconciling it against milestones.
- You run two or more legal entities where at least one is FCA-regulated and consolidation is manual
- Your revenue is time-based or retainer-based and standard ERP revenue recognition fights it
- Month-end close consistently exceeds a week because of intercompany or FX adjustments
- Project profitability lives outside the ERP in spreadsheets nobody trusts
- You're a single-entity firm with straightforward GBP billing and no regulated arm
- NetSuite or Dynamics already closes your books in under four days
- Your revenue model is simple product or subscription with no deferred media or disbursements
- You lack internal finance capacity to spec and test a custom consolidation engine
- Month-end close drops from 11 days to 3 to 4 because intercompany eliminations and FX revaluation run as coded rules, not manual journals
- Real-time project profitability across billed time, cost, and recoverable disbursements feeds straight from your time-tracking system
- The FCA-regulated entity stays cleanly ring-fenced for reporting without three separate exports
- Revenue recognition for retainers and deferred media follows your contracts automatically, audit-ready
- One consolidated view your CFO trusts on day three, not a spreadsheet they rebuild every quarter
- A custom consolidation engine needs ongoing maintenance as FRS 102 and FCA reporting rules change; budget for a retainer
- You take on responsibility for tax-table and VAT-logic updates that NetSuite would have shipped for you
- Migration of historic ledgers from SAP or Dynamics is genuinely hard and where most of the timeline risk sits
- If your group is stable and single-entity, you may be paying for flexibility you'll never use
The honest cost picture for London
| Project scope | Typical cost | Timeline |
|---|---|---|
| Custom consolidation + reporting layer on top of existing ERP | £70k to £130k | 4 to 6 months |
| Full custom ERP for multi-entity London services group | £160k to £260k | 7 to 9 months |
| Project-revenue and time-to-billing module only | £45k to £85k | 3 to 4 months |
Feature priorities for London teams
London ERP: the full scope
The engagements London teams bring us most often: NetSuite customization, SAP integration, Odoo development, Microsoft Dynamics 365, ERP migration, cloud ERP and manufacturing ERP.
Exactly what you get
A consolidation and reporting layer that sits over your existing NetSuite, SAP, or Dynamics GL and does the work your finance team does by hand: automated intercompany eliminations across your London entities, scheduled FX revaluation on USD and EUR balances, project-level profitability fed from time-tracking, and an FCA-entity reporting pack that exports clean. You keep the packaged ledger where it earns its keep and replace only the month-end spreadsheet chaos with coded rules your auditor can trace.
How to choose a developer in London
Hire a team that has shipped finance systems for a regulated London group, not just an e-commerce store. Ask them to walk you through how they'd model your weakest reconciliation, the one that eats the most days at close. The right partner talks about FRS 102, intercompany logic, and your real chart of accounts in the first meeting. The wrong one talks about dashboards. Pair the ERP work with your CRM (Customer Relationship Management), accounting software, and business intelligence dashboard plans so the consolidation has clean data flowing in from day one.
Timeline: what happens, and when
- !They quote a fixed price before seeing your intercompany structure; ask how they handle FCA-entity eliminations specifically
- !No one on the team has touched FRS 102 consolidation; ask for a London services-group reference
- !They propose rebuilding your GL from scratch; ask why they won't keep what works in NetSuite
- !Migration is hand-waved as 'we'll import the CSVs'; ask for their reconciliation test plan
- !They can't explain how they'll handle USD/EUR FX revaluation; ask to see the journal logic
If erp is on the roadmap, internal tools, shopify, inventory management usually follow within the year. Budget them as one conversation.
Rohan advises mid-market and enterprise teams on ERP, CRM and custom software, and has led delivery on dozens of business-software builds.
Writes for Digital Heroes, shipping business software for 2,000+ brands across 55+ countries since 2017.
Frequently asked questions
Can I keep NetSuite and still build custom?
Yes, and for most London groups that's the right call. You keep NetSuite as the transactional GL and build a custom consolidation, FX, and project-revenue layer on top. It's cheaper and faster than a full replacement and avoids re-migrating data that already works.
How long does a custom ERP build take for a London firm?
Five to nine months end to end. A consolidation-only layer over an existing ERP lands in four to six; a full multi-entity build for a regulated group runs seven to nine, with most of the risk in migrating historic SAP or Dynamics ledgers.
Why won't off-the-shelf ERP handle our agency revenue?
Packaged ERPs model product and subscription revenue well but struggle with time-based retainers, deferred media spend, and recoverable disbursements. London agencies and services firms end up booking those by hand every month, which is exactly what custom revenue-recognition logic eliminates.
What does FCA-entity ring-fencing actually require?
Your regulated entity needs to report on its own permissions and capital position without contamination from the unregulated arms. A custom ERP keeps those entities cleanly separated in the consolidation so you can produce the regulated pack without three manual exports.
Is this worth it under £100k of finance overhead?
If your close is under four days and you're single-entity, probably not. The case strengthens fast once you have two or more entities, a regulated arm, and a month-end that needs a spreadsheet rescue. That's when the manual reconciliation cost outruns the build.