Professional services firms lose a surprising amount of revenue to unbilled time. Hours get forgotten, entries sit unapproved, invoices go out late, and the gap between work done and fees collected quietly widens. Most firms know this. The usual response is to buy a SaaS time and billing tool, only to discover it does not handle your billing model, does not connect properly to your accounting software, and leaves your team maintaining spreadsheets alongside the “official” system.
We build custom time and billing software for UK professional services firms. It encodes your actual billing rules, integrates directly with the tools you already use, and belongs to you outright. No per-user fees that scale with every hire. No workarounds for billing logic the vendor did not anticipate.
Why off-the-shelf time and billing software falls short
The SaaS market is crowded with options, from free tools like Clockify to full professional services automation platforms. They all share a common problem: they are built for the average firm, not yours.
Here is what that looks like in practice:
- Rigid billing models. Most tools handle hourly billing well enough. But blended rates, retainer drawdown, contingency multipliers, success-based fees, or client-specific rate cards with role and seniority tiers? You end up with manual adjustments on every invoice.
- Per-user pricing that compounds. At £8 to £40 per user per month, costs escalate fast as you grow. Adding part-time or temporary staff becomes a budget discussion rather than a workflow decision. A 50-person firm can easily spend £12,000 to £24,000 a year on subscriptions alone.
- Weak accounting integration. Invoices exported to Xero or QuickBooks in batches introduce lag. Rate changes in one system do not reflect in the other. Trust account reconciliation, if supported at all, requires parallel spreadsheets.
- Single-level approval workflows. Real firms need multi-tier sign-off: partner, then manager, then finance. SaaS tools typically offer one approval step, with no conditional routing based on project value or client.
- Bolted-on UK compliance. Making Tax Digital support varies widely. Multi-rate VAT, SRA Accounts Rules for solicitors, IOLTA trust accounting, and proper GDPR audit trails are afterthoughts if they exist. Invoice retention for the required six years is your problem to manage.
- Reporting that cannot answer your questions. Fixed report templates with no drill-down. No realization rate, no utilization percentage, no margin by project phase. You export to Excel and build the analysis yourself.
- Approval workflows that break down. When the software cannot model your sign-off process, staff resort to email approvals. The audit trail disappears. Invoices pile up waiting for the right person to approve them through the wrong channel.
The result is predictable: the SaaS tool handles time entry, but everything around it, the billing logic, the approvals, the reporting, the compliance, lives in spreadsheets and email chains.
What we build instead
Your billing rules, encoded
We do not ask you to simplify your billing model to fit our software. Whether you bill hourly with partner and associate rate tiers, run retainers with drawdown tracking, use flat fees per phase, or apply contingency multipliers, we build the logic into the system. Rate cards can vary by client, role, seniority, and time period.
Direct accounting integration
We build API-level integrations with Xero, QuickBooks, and Sage so that clients, invoices, and payments sync in both directions without manual exports. Rate changes propagate automatically. No batch exports, no reconciliation spreadsheets.
Approval workflows that match your firm
Multi-tier approval cascades with conditional routing. Route time entries and invoices to different approvers based on project, client, value threshold, or practice area. Every approval is logged with who approved, when, and any annotations or write-off notes.
UK compliance from day one
Making Tax Digital integration with HMRC API connectivity. Multi-rate VAT handling across standard, reduced, zero-rated, and exempt supplies. Full GDPR audit trails recording every data access and change. For legal firms, SRA-compliant record keeping and trust account reconciliation. Six-year data retention built into the architecture.
You own it
No per-user licensing. No annual price increases. No vendor lock-in. The code and data are yours. If you want to modify the system, extend it, or move it to different hosting, you can.
It grows with your firm
The architecture is modular. Start with time entry, approvals, and invoicing. Add expense tracking, a client portal, capacity planning, or multi-entity consolidation later without rebuilding what already works.
Core features
Every build is different, but most time and billing projects include modules from this list:
Time capture
- One-click timers and manual time entry
- Billable and non-billable classification
- Activity codes (ABA codes for legal, custom codes for other sectors)
- Calendar sync with Google Calendar and Outlook
- Mobile-friendly time entry with offline support
- Duplicate entry detection and time entry reminders
Billing and invoicing
- Configurable billing rules: hourly, flat fee, retainer with drawdown, contingency, milestone-based
- Role-based and client-specific rate cards with effective date versioning
- Pre-bill review with batch approval
- Custom invoice templates with your branding, VAT breakdown, and payment terms
- Recurring invoice generation
- Multi-currency support where needed
- LEDES format export for legal firms with corporate clients
Approvals
- Multi-tier approval workflows (e.g. partner, manager, finance)
- Conditional routing by project, client, or invoice value
- Approval annotations for write-offs, adjustments, and rush fees
- Full approval chain audit trail
Client and project management
- Client records with billing addresses, VAT IDs, payment terms, and credit limits
- Project setup with budgets, phases, and billing type per phase
- Retainer balance tracking and replenishment alerts
- Project profitability monitoring against budget
Reporting and dashboards
- Billable utilization by team member, role, and department
- Realization rate (fees billed versus hours worked at standard rate)
- Project margin and margin by phase
- Unbilled time ageing
- Invoice ageing and payment status
- Revenue forecasting
- Drill-down dashboards rather than static PDF exports
- Scheduled report delivery by email
Integrations
- Xero, QuickBooks, and Sage (bi-directional API sync)
- Stripe, PayPal, or GoCardless for online payment collection
- HubSpot, Salesforce, or Pipedrive (CRM)
- Jira, Asana, Monday.com, or Trello (project management)
- Slack or Microsoft Teams (notifications)
- Google Workspace and Microsoft 365 (calendar and email)
- REST API and webhooks for custom connections
Compliance and security
- GDPR audit trails (who accessed what, when, from where)
- Making Tax Digital API integration
- Multi-rate VAT invoicing
- SRA and Law Society compliance features for solicitors
- Trust accounting with IOLTA reconciliation for legal firms
- Role-based access control with two-factor authentication
- Data retention policies with auto-deletion
- UK data hosting options
How a project works
Phase 1: Discovery and planning (2 to 3 weeks)
We interview your finance team, project managers, and partners to map current workflows, identify where time leaks and billing bottlenecks occur, and define integration requirements. We audit your existing data to understand migration complexity: how many years of history, how consistent the client and project records are, and what rate card structures need to be carried across.
The output is a project roadmap with clear milestones and a defined MVP scope.
Phase 2: Build (8 to 12 weeks for MVP)
We develop iteratively with fortnightly demos so you can steer the build. A typical MVP covers:
- User authentication and role-based access
- Client and project management
- Time entry with timers and manual input
- Single-level approval (manager sign-off)
- Hourly billing with invoice PDF generation
- Billable time reporting by project and team member
- CSV export for accounting software import
From there, we add complexity in order: retainer and flat-fee billing logic, multi-tier approvals, native accounting API integration, expense tracking, advanced reporting, and a client-facing portal.
Phase 3: Testing and migration (2 to 4 weeks)
We run thorough QA across billing scenarios including edge cases like split billing, write-offs, and mid-project rate changes. We migrate your historical data, running a parallel period where both systems operate so your team can validate outputs before the old system is switched off.
Phase 4: Training and go-live
We train each user group according to their role. Finance staff get the deepest training on invoice generation, approval workflows, and reporting. Individual contributors get focused sessions on time entry. We provide written documentation and video walkthroughs, and we stage the rollout so your entire team is not disrupted at once.
Ongoing support
UK-based support from the team that built your system. We offer flexible support arrangements for bug fixes, minor enhancements, and larger feature additions as your firm evolves.
What it costs
A custom build costs more upfront than a SaaS subscription. The trade-off is that you own the result and pay nothing per user.
For context: a 25-person firm using a mid-range SaaS tool at £20 per user per month spends roughly £6,000 a year on subscriptions, or about £30,000 over five years, before accounting for setup fees, premium support charges, data migration costs, or the price increases that SaaS vendors routinely apply.
A custom MVP for a firm of that size typically starts in the region of £30,000 to £55,000 for the initial build, with ongoing support and enhancements costing significantly less than annual SaaS renewals. For larger firms, or those with complex billing logic, trust accounting, or multi-entity requirements, the scope and cost are higher, but the per-user economics tilt further in favour of custom.
The honest answer: for a small team with straightforward hourly billing and no compliance requirements beyond GDPR, a SaaS tool like Harvest or Clockify is probably sufficient. Custom makes sense when your billing logic is non-standard, your approval workflows have multiple tiers, you need tight integration with legacy systems, or per-user pricing is becoming a significant line item.
We scope every project with a free consultation and provide a fixed quote before any work begins.
Industries we work with
Law firms
Matter-based time tracking with billable and non-billable classification. Multiple billing models across the same practice: hourly with partner and associate rate tiers, flat-fee for routine work, contingency for litigation, retainers for ongoing advisory. Trust accounting with IOLTA reconciliation, SRA Accounts Rules compliance, ABA activity codes, and LEDES format invoice export for corporate clients with e-billing mandates. Typical targets: 70 to 80 percent billable utilization for associates, realization rate tracking, and days sales outstanding under 60 days.
Accounting practices
Time tracked across engagement types: audit, tax preparation, bookkeeping, and advisory. Client rate hierarchies reflecting partner, manager, senior, and junior billing rates. Project profitability by engagement type. Unbilled time ageing with a target of less than seven days. CPE time tracking linked to ICAEW requirements. VAT-compliant invoicing and MTD integration.
Architecture and engineering firms
Phase-gated billing aligned with RIBA Plan of Work or equivalent project stages. Time allocated across concept, schematic design, design development, and construction documentation. Labour costs, subconsultant fees, and reimbursable expenses tracked against project budgets. Milestone-based invoicing triggered by phase completion. Resource allocation across multiple concurrent projects.
IT services and managed service providers
Fixed monthly fees for SLA-covered services alongside time-and-materials billing for project work and change orders. Automated billing against service contracts. Utilization forecasting to identify capacity for upsell. Cybersecurity audit trails where handling regulated client data. Blended billing across recurring and one-off engagements.
Consulting firms
Client engagement tracking across multi-phase projects with different billing structures per phase. Retainer management with drawdown tracking and replenishment alerts. Resource allocation and bench management. Utilization and realization rate reporting by consultant. Contract compliance checks to ensure billing aligns with statement of work terms.
Creative agencies and studios
Per-client billing structures with project-based time tracking. Milestone-based invoicing for campaign or project deliverables. Approval workflows with client sign-off stages. Blended teams with different rates for strategy, design, and production roles. Budget monitoring against agreed project fees.
Each of these sectors has billing workflows that generic software either handles clumsily or ignores entirely. That is the practical case for building something that fits.
Common Questions About Custom Time and Billing Software for UK Professional Services
How does the cost of a custom build compare to SaaS time and billing tools?
SaaS tools like Harvest or Productive typically cost between £8 and £40 per user per month. For a 25-person firm, that works out to roughly £22,000 to £35,000 over three years. A custom build has a higher upfront cost, but you own the result outright with no per-user fees. For teams of 40 or more, or firms with complex billing logic that forces workarounds in SaaS tools, custom usually breaks even within two to three years and becomes significantly cheaper over five.
What is the typical development timeline?
An MVP covering time entry, one-level approvals, hourly billing, invoice generation, and CSV export to your accounting software takes roughly 8 to 12 weeks. Adding retainer billing, multi-tier approval workflows, native Xero or QuickBooks API integration, and a client portal typically extends that to 12 to 16 weeks. Trust accounting, multi-entity consolidation, or advanced compliance features for regulated firms may take 20 weeks or more.
Can you integrate with Xero, QuickBooks, or Sage?
Yes. We build direct API integrations with Xero, QuickBooks Online, and Sage so that invoices, payments, and client records sync automatically. No CSV exports, no manual reconciliation. We also integrate with project management tools like Jira, Asana, and Monday.com, CRM systems like HubSpot or Salesforce, and calendar platforms like Google Calendar and Outlook.
What about Making Tax Digital and GDPR?
MTD compliance is built in from the start, including digital record keeping, multi-rate VAT support (20%, 5%, 0%, and exempt), and API connectivity to HMRC. For GDPR, we implement full audit trails recording who accessed or changed data and when, data export in machine-readable formats, and retention policies with auto-deletion. For law firms, we can also handle SRA Accounts Rules compliance and trust account reconciliation.
How do you handle data migration from our existing system?
We export your client records, project data, rate cards, and historical time entries from your current system, clean and deduplicate the data, and import it into the new build. We run a parallel period where both systems operate side by side so your team can validate invoices and reports before the old system is switched off. Most migrations take two to three weeks depending on data volume and how consistent the existing records are.
Do you provide training for our team?
Yes. Training is included in every project. Finance and billing staff typically need four to eight hours covering invoice generation, approval workflows, and reporting. Project managers need two to four hours. Individual contributors usually need one to two hours on time entry and expense submission. We provide written documentation and video guides for common tasks, with optional refresher sessions after go-live.