Work out what you owe across overdue tax years
We reconcile income, allowable expenses, tax already paid and HMRC notices. The aim is a supported calculation for each year, with assumptions and missing records identified.
Your fixed quote
Tell us your situation and we come back within 48 hours with a fixed written quote. No obligation.
Back Tax Calculation: What You Need to Know
We reconcile income, allowable expenses, tax already paid and HMRC notices. The aim is a supported calculation for each year, with assumptions and missing records identified.
Start with the relevant guide or use the free estimate or deadline tool. If you need help applying that information to your records, request a quote and include any urgent notice date.
Before acting as your agent, we agree the engagement and the HMRC authorisation needed. Keep responsibility for urgent deadlines in view while that process is completed.
Back-tax work is about reconstructing a supported liability, not adding a percentage to a previous bill. We separate income tax or company tax from filing penalties, payment penalties and interest, then reconcile tax deducted, credits and payments. Each figure should have an identifiable source.
Benefits of Back Tax Calculation
A defined scope
The quote identifies the years, returns or notices covered and what information is still needed.
Records behind the figures
We distinguish confirmed information from assumptions, estimates and missing evidence.
Separate filing and payment decisions
Submitting a return does not pay the tax or cancel existing penalties. Each issue needs its own next step.
What you should receive from a reconstruction
Expect a year-by-year calculation with the source records, assumptions and unresolved gaps identified. An apparent overpayment does not guarantee a refund: claim conditions and time limits must be checked.
HMRC interest is daily simple interest on the relevant unpaid balance using the rates applicable over time. A single-rate online estimate cannot replace reconciliation of historical payments and rates.
Is Back Tax Calculation Right for Your Situation?
This service may help if you have:
- An HMRC estimate or determination that needs comparing with actual records
- Historic income, expenses or losses that have not been reconciled
- Uncertainty about the tax balance before filing or proposing payment
An initial consultation is always the right starting point. We review your HMRC records, assess your penalty position, and give you a clear recommendation based on your specific circumstances.
How the Process Works
Gather year-by-year records
List the years, income sources, relevant HMRC statements and records available.
Check income and allowable reliefs
Apply the rules for each year and check allowable expenses, reliefs, losses and their claim deadlines.
Reconcile payments and HMRC charges
Compare calculated liabilities with tax deducted, payments, credits and separately assessed charges.
Explain the figures and next steps
Explain the calculation, unresolved assumptions and which returns, amendments or claims may be needed next.
Back Tax Calculation Pricing Guide
Fees depend on the complexity of your situation. We provide a fixed written quote within 48 hours of your enquiry so you know exactly what you will pay before committing.
Every Day Costs You More
HMRC penalties start at £100 and increase by £10 per day after 3 months. The longer you wait, the more you pay. Tell us what is outstanding and get a fixed written quote today.
What We Handle for You
- Return preparation, HMRC submission, basic penalty advice
- Penalty review, excuse preparation, HMRC correspondence, follow-up
- All years preparation, coordinated submissions, penalty minimisation strategy
- Evidence gathering, claim preparation, HMRC submission, response handling
- Financial analysis, HMRC negotiation, payment plan setup, ongoing support
- Historic analysis, interest calculation, penalty computation, summary report
Back Tax Calculation FAQs
Common Situations We Resolve
One or two years overdue
Self-employed income, rental property, or a one-off capital gain that should have been reported. We file the outstanding returns, calculate the true liability, and apply any reliefs that reduce what is actually owed.
Penalty notice just arrived
The 30-day appeal window is running. We assess whether a reasonable excuse claim has genuine merit, prepare the appeal with supporting evidence, and present it in the format HMRC accepts.
Multiple years behind
Three, four, or more years of unfiled returns. We reconstruct records from bank statements and HMRC data, file everything in the right order, and negotiate penalty mitigation across the whole period.