Private practice, locum sessions, medico-legal fees or a rental property that never reached a tax return: in almost every case the answer is to come forward now through HMRC's Digital Disclosure Service rather than wait. The reason is arithmetic rather than conscience. A disclosure made before you have any reason to believe HMRC has discovered the problem is unprompted, and for careless behaviour the penalty range then starts at 0% of the tax. Once HMRC writes to you the same disclosure is prompted, and the range starts at 15%. For deliberate behaviour the floors are 20% unprompted and 35% prompted. How far back you have to go is set by behaviour too: four years where you took reasonable care, six years where you were careless, twenty years where the shortfall was deliberate. Interest is charged daily from the date each year's tax fell due and is not reduced by coming forward, so it grows while you decide. If you cannot pay in one go, time to pay is discussed with HMRC before the disclosure goes in. The one thing that changes all of this is a letter from HMRC, and that is outside your control.
How many years do you have to go back?
Four, six or twenty, decided by how the shortfall came about. The ordinary assessing time limit is four years from the end of the year of assessment. Where the loss of tax was brought about carelessly by you or someone acting on your behalf, section 36(1) of the Taxes Management Act 1970 extends that to six years. Where it was brought about deliberately, section 36(1A) extends it to twenty. HMRC's own guidance on making a disclosure uses exactly those three figures, so this is not a point of argument between you and an inspector.
The mechanism HMRC uses to assess a closed year is the discovery assessment in section 29 of the same Act. That is why a year you thought was finished can be reopened at all, and why the honest classification of your own behaviour matters more than any other decision in the process. A doctor who describes a genuine oversight as careless and pays six years is in a very different position from one who describes deliberate omission as careless and is later found out.
What does the penalty actually come to?
A percentage of the tax, inside a range set by behaviour and then narrowed by whether the disclosure was unprompted. Inaccuracies in a return are penalised under Schedule 24 to the Finance Act 2007, and HMRC publishes the ranges in factsheet CC/FS7A.
| Behaviour | Unprompted disclosure | Prompted disclosure |
|---|---|---|
| Careless | 0% to 30% | 15% to 30% |
| Deliberate, not concealed | 20% to 70% | 35% to 70% |
| Deliberate and concealed | 30% to 100% | 50% to 100% |
Where you never registered for self assessment in the first place, the failure is penalised under Schedule 41 to the Finance Act 2008 instead. For a non-deliberate failure to notify the unprompted range is 0% to 30% if you disclose within 12 months of the tax becoming due and 10% to 30% after that, and the prompted range is 10% to 30% within 12 months and 20% to 30% after. The deliberate bands match the table above.
Where you land inside a range depends on the quality of the disclosure, which HMRC splits three ways: telling, worth up to 30% of the available reduction, helping, worth up to 40%, and giving access to records, worth up to 30%. That is why a disclosure built from reconstructed bank statements, appointment records and agency remittances lands lower than one that leaves HMRC to do the work.
How does the Digital Disclosure Service work in practice?
You notify first, then you disclose. Step one is telling HMRC through the online service that you intend to make a disclosure. HMRC acknowledges that and issues a disclosure reference number. Step two is the disclosure itself, and you have 90 days from the date of the acknowledgement to calculate the tax, interest and penalty, submit the figures and pay.
The practical consequence is that the notification starts a clock you cannot extend at will, so the reconstruction work belongs before the notification, not after it. Gather the years first: private clinic remittances, agency statements, insurer payments, medico-legal invoices, bank credits that never matched a payslip. HMRC will not accept a disclosure found to be largely wrong or incomplete when it is checked, and a rejected disclosure is worse than a slow one.
What about interest and paying it?
Interest runs daily from the date the tax for each year was originally due until the day it is paid. It is compensation for late payment rather than a sanction, so unlike the penalty it is not reduced by coming forward. On a shortfall spread over six years, the interest on the earliest year has been accruing for most of a decade, and it is usually the element doctors underestimate when they postpone the decision.
If you cannot pay in full, HMRC asks you to call the disclosure helpline as soon as possible and before you send the disclosure in, so that time to pay is arranged alongside it rather than chased afterwards. A time to pay arrangement changes the schedule, not the amount.
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When is the Digital Disclosure Service the wrong route?
Where the behaviour amounts to tax fraud. HMRC runs a separate facility for that, the Contractual Disclosure Facility under Code of Practice 9, requested on form CDF1, which covers deliberate behaviour only and not errors or mistakes. Choosing the wrong facility is not a neutral mistake, so where the honest label is in doubt a specialist reviews the history and the classification before anything is notified.
Where does this usually start for a doctor?
Rarely with anything dramatic. The common shapes are private sessions paid gross alongside a salaried post, locum work through an agency where the tax was assumed to have been handled, insurer or medico-legal fees paid into a personal account, and a first year of private work where registration for self assessment was simply missed. If your position is that private income was declared but expenses or years were handled loosely, the starting point is how NHS and private income sit together on a return and what was actually claimable.
For locums, the two pages worth reading alongside this one are the locum self assessment filing guide and what a locum can claim, because a disclosure that omits legitimate expenses overstates the tax and therefore overstates the penalty as well. Reconstructing the deductions is part of the disclosure, not a separate exercise for later.
So what should you do this week?
Work out, roughly, which years are affected and which behaviour label honestly fits. That single judgement sets the number of years, the penalty band and the facility you use. Then reconstruct the figures before notifying, because notifying starts the 90 days. The one thing not worth doing is waiting to see whether HMRC notices, because the day a letter arrives your disclosure becomes prompted and the cheapest outcome available to you is no longer on the table.