Payroll software is one of those things businesses tend to settle for. You pick a package, twist your workflows around it, pay the monthly fee, and put up with the bits that don’t quite fit. After a few years the subscription is one of your bigger line items, and the system still doesn’t do the one thing you’ve been asking about since month two.
I build custom payroll systems instead. Yours, not rented. Designed around the way your team runs payroll, with the integrations you need and the reporting you’ve been doing in spreadsheets because the SaaS tool wouldn’t.
HMRC quirks aren’t exotic to me: RTI submissions, auto-enrolment, CIS, the apprenticeship levy, term-time pay, NHS pension schemes, student loan plans, statutory sick and maternity pay. If your payroll software has become a tax on your finance team’s time, this is the conversation worth having.
Why off-the-shelf payroll software keeps disappointing UK businesses
For a single-entity business with standard pay, stable headcount and no awkward approval rules, a SaaS product is usually the right call, and I’ll tell you so. The trouble starts when your payroll stops being standard. The same patterns come up whenever I sit down with a finance director:
- The software dictates the workflow, so people do extra steps to keep it happy
- Approval chains are hardcoded. There’s no clean way to say “anything over this amount needs the CFO” or to route sign-off by cost centre
- Commission, bonuses, retro-pay, reversals and one-off deductions live in spreadsheets because the platform assumes everyone is salaried or hourly
- Per-employee pricing scales badly, and the renewal quote grows with every hire
- Connecting it to your accounting package, HR system or time-and-attendance kit turns into a project of its own, and the payroll-to-ledger posting still lags or duplicates
- Some international platforms treat RTI, auto-enrolment edge cases and CIS as afterthoughts, so UK filing needs a bridge or a manual workaround
- HMRC changes the rules and the vendor’s update lands later than you’d like
The licence fee is usually the smallest part of the cost. The bigger one is the manual work that builds up around the software’s gaps. Implementation, data migration and integration fees often exceed the headline subscription, and they rarely appear on the pricing page.
A custom build earns its keep when the awkwardness is real and ongoing: non-standard pay structures, approval rules tied to your governance, multiple legal entities, tight integration with a finance system you can’t easily replace, or data residency constraints.
What changes when payroll is built for you
Designed around how you work
I start by watching a pay run, asking awkward questions and mapping what already works. The software then supports those habits rather than replacing them, and your approval workflow can match your org chart, not the other way round.
Pay once, own it
You commission the system, I build it, you own it. No per-employee monthly fees ticking up as you grow, no minimum contract term, no early-exit penalty, and no data trapped in a proprietary format if you ever want to move on. The code is yours.
Built to talk to your other systems
Xero, Sage, QuickBooks, your HR platform, time-and-attendance kit, your bank’s BACS files: I wire them up so data only gets entered once. Payroll posts straight to the general ledger with the journal structure your accountants use.
HMRC compliance handled
PAYE, National Insurance, RTI submissions (Full Payment Submission and Employer Payment Summary), pension auto-enrolment including the three-year re-enrolment cycle, P45s, P60s, P11Ds, CIS, and the apprenticeship levy where it applies. When legislation changes, the system is updated.
Built to scale with you
A new entity, pay structure or bonus scheme is a configuration change or a small build, not a replacement system. Per-employee pricing doesn’t punish you for hiring.
Support from the person who built it
When something needs sorting, you deal with the developer who built your system, not a support queue during the busiest week of the tax year.
What a typical custom payroll system includes
Every build is shaped around your requirements. I ship a working core first, then add the rest in a second phase once it’s live and stable.
The core build covers:
- Gross-to-net calculation of salaries, tax, NI, pension contributions and statutory deductions, driven by each employee’s tax code and NI category
- Configurable salary structures and pay rules, including allowances such as London weighting and on-call, and conditional or project-linked deductions
- Batch payroll runs (weekly, fortnightly, monthly) with clear status tracking through draft, approved and paid
- BACS payment file generation and payslip distribution
- Direct HMRC filing for RTI, plus P45s, P60s and P11Ds
- Approval workflows that match how authorisation happens in your business, including conditional sign-off by amount or cost centre
- General-ledger posting into your accounting package, with reconciliation reports
- Audit trails and role-based, UK GDPR-compliant data handling
A second phase commonly adds:
- An employee self-service portal for payslips, P60s, leave requests and personal detail updates
- Time-and-attendance integration so hours feed payroll without manual rekeying
- Multi-entity payroll for groups running several companies or subsidiaries
- Commission and bonus calculation pulled from sales or performance data, including clawback and multi-tier rules
- A finance dashboard: payroll cost trends, headcount, overtime patterns, tax liability
- Mobile access for approvals and reporting
Automated payroll: RTI, FPS and the rest of the pay run
Most of a UK pay run is the same steps in the same order every period, and every one of them has a deadline. An automated payroll system runs those steps itself and stops for a person only where judgement is needed.
| Step | What the system does | The rule it works to |
|---|---|---|
| Hours and changes | Pulls approved hours, overtime and shift premiums from your rota or clocking system, plus starters, leavers and pay changes from HR | Only approved records go in |
| Tax codes | Downloads tax code and student loan notices from HMRC’s Data Provisioning Service and applies them | HMRC issues the notices; nobody rekeys them |
| Exceptions | Flags anything outside the thresholds you set, such as net pay moving more than a set amount on last period, a negative net pay or a missing bank detail | A reviewer clears the flags before approval |
| Calculation and payment | After sign-off, runs gross-to-net, issues payslips and produces the BACS file | Approval is recorded against the run |
| Full Payment Submission | Builds and sends the FPS, stores HMRC’s acknowledgement with the run and alerts you if a submission is rejected | HMRC requires the FPS on or before payday |
| Employer Payment Summary | Prepares the EPS for recoverable statutory pay, Employment Allowance or CIS deductions suffered | Due by the 19th after the end of the tax month |
| Pensions | Sends contribution files to your provider, such as NEST or The People’s Pension, and assesses new joiners for auto-enrolment | Contributions on qualifying earnings, re-enrolment every three years |
| Accounts | Posts wages, tax, NI and pension costs to Xero, Sage or QuickBooks by cost centre | Journal matches your chart of accounts |
| Year end | Sends the final FPS of the year and issues P60s | P60s to employees by 31 May |
Before the first live submission, the software is tested against HMRC’s test service. Records are kept to HMRC’s rule of three years from the end of the tax year they relate to, and auto-enrolment records for the six years The Pensions Regulator expects.
Automation doesn’t remove the approval. It moves your payroll lead’s time from keying and checking every line to reviewing the handful of exceptions the system raises.
How I build it
First Gear, 5 days
I sit with your payroll team, your finance lead and whoever owns the integrations. I document the current process, the friction points and the bespoke deductions hiding in spreadsheets. You get a working prototype on your own data, a one-page build plan and a fixed price.
Build
I do the work, bringing in a trusted specialist where a part of the job needs one. You see progress as it lands, push back on the bits that don’t feel right, and I adjust. The core payroll engine comes first so there’s something real to test against.
Migration, testing and rollout
Migration is the part that catches most projects out. Year-to-date balances, historical payroll, employee master data, deductions and leave balances all have to come across cleanly, and legacy data rarely is. I audit and cleanse it, reconcile year-to-date totals against your ledger and last P60s, then run at least one pay cycle in parallel with your existing system until the numbers match exactly. Only then do we cut over, and never close to month-end or tax year-end. The old system stays available as a fallback until the new one is proven.
Training and support
I train your team in person or remotely and document everything. Payroll staff need the most hands-on time; managers approving runs need an hour or two. After the 30-day fix guarantee and the free first month of hosting, a monthly plan is optional.
What it costs
Custom development costs more up front than signing up to a SaaS product. The maths only works if you keep the system for a few years, which most businesses do.
Per-employee SaaS payroll typically charges a base fee plus a monthly amount per head, which is fine at small scale and compounds as you hire. You own none of it, and setup, migration, integration and tax-filing fees often don’t show on the pricing page. A custom build has its price fixed in the build plan; multi-entity systems with complex pay rules are split into phases.
What you get back:
- Less time lost to payroll admin once calculation, RTI and ledger posting are automated
- Fewer calculation errors and fewer reconciliation mismatches
- No “we’d need to upgrade your plan for that” conversations when you want a new feature
- No per-employee pricing penalty as you grow, and no multi-year lock-in
- Software that’s yours, code included
If SaaS is the better-value choice for your situation, I’ll say so.
Sectors and situations I build for
The pattern of “off-the-shelf doesn’t quite fit” looks different in each industry:
- Construction handling CIS verification and returns, subcontractor payments, mixed PAYE and CIS workforces, and payroll allocated to project codes for job costing
- Healthcare and social care with rotating and on-call shift patterns, agency and locum rates, NHS pension schemes and cost allocation across wards or care homes
- Hospitality and retail running variable-hour rotas, split shifts and zero-hours staff, plus tip distribution under the Employment (Allocation of Tips) Act 2023, which requires a written tipping policy and tip records
- Manufacturing tying payroll to time-and-attendance and production data, including shift premiums and piece-rate pay
- Education with term-time-only contracts, variable hours and research-grant cost allocation
- Professional and financial services with mixed employee and contractor payments, partner draws, profit-share and variable compensation
- Charities allocating payroll across restricted funding streams and grants
- Multi-site groups and franchises consolidating payroll across several entities into one reporting view
- Payroll bureaux and accountants who want to run payroll as a service for their own clients on software they own
Common trigger points: the pay run depends on a spreadsheet only one person understands; you’ve added a second legal entity; an RTI error or HMRC enquiry has exposed a control gap; payroll and your accounts have drifted out of sync; or your payroll specialist has left and taken the undocumented process with them.
Common Questions About Custom Payroll Management Systems
How does a custom payroll build compare on cost to SaaS? ›
A custom build costs more up front. The trade-off is that you stop paying per-employee fees that never end. Most builds cost £2k-£10k, at a fixed price agreed at the end of First Gear. Complex multi-entity systems are split into phases. Whether it pays back depends on your headcount and how badly off-the-shelf software fits, which I work through with you in First Gear rather than promising a break-even date.
What's the typical development timeline? ›
Most single-entity first releases go live within a month. I ship a working core first (calculation, RTI, payslips, ledger posting), then add self-service, time-and-attendance integration or advanced reporting in a second phase. Multi-entity payroll or unusual pay structures add phases, each about a month of work.
What can an automated payroll system run without someone keying it in? ›
Pulling approved hours from your rota or clocking system, gross-to-net calculation, payslips, the BACS file, the Full Payment Submission to HMRC, the monthly Employer Payment Summary, pension contribution files and the journal to your accounts. A person still reviews the flagged exceptions and approves the run before anything is paid or filed.
Will the system handle HMRC RTI and pension auto-enrolment? ›
Yes. Full Payment Submissions and Employer Payment Summaries are built to HMRC's required format, along with P45s, P60s and P11Ds. Auto-enrolment is handled end to end, including assessment, contributions and the three-year re-enrolment cycle. Where relevant I also cover the apprenticeship levy, student loan plans and statutory sick, maternity, paternity and shared parental pay.
Can you integrate with our accounting and time-tracking systems? ›
Yes. I commonly connect payroll to Xero, Sage, QuickBooks and other accounting packages so payroll posts straight to the general ledger, plus HR systems, time-and-attendance tools and your bank's BACS payment files. Data is entered once, and the month-end reconciliation most finance teams dread mostly disappears.
What happens with annual tax changes and ongoing support? ›
Every build includes a 30-day fix guarantee and the first month of hosting free. After that, an optional monthly plan covers updates when legislation changes (NI thresholds, tax bands, minimum wage rates, pension contribution rules), or you can commission work as you need it. Because you own the code, you aren't waiting on a vendor's release schedule when HMRC changes the rules.
How do you handle data security and GDPR? ›
Payroll data is some of the most sensitive your business holds: bank details, tax codes, National Insurance numbers. Systems are built with role-based access, encryption in transit and at rest, and full audit trails of who changed what and when. I can deploy on UK or EU infrastructure where data residency matters, and you remain the data controller.
Can you migrate our existing payroll data? ›
Yes, and I treat it as the riskiest part of the project. Year-to-date balances, historical payroll, employee master records, deductions and leave balances all have to come across cleanly. Legacy data is rarely tidy, so I budget time for cleansing and reconciliation, and run the new system in parallel with your old one until the numbers match exactly before cutover.