CIS Late Filing Penalty and Appeal Estimator
HMRC charges a fixed penalty for every CIS300 monthly return filed late, and the amount rises the longer it remains outstanding. This tool works out your total penalty exposure, applies the £3,000 new-contractor cap where it is due, shows you the per-return breakdown and flags whether an appeal on reasonable-excuse or nil-return grounds is worth making.
CIS Late Filing Penalty and Appeal Estimator
HMRC charges a fixed penalty for every CIS300 monthly return filed late, and the amount rises the longer it remains outstanding. This tool works out your total penalty exposure, applies the £3,000 new-contractor cap where it is due, shows you the per-return breakdown and flags whether an appeal on reasonable-excuse or nil-return grounds is worth making.
Each overdue CIS300 monthly return carries its own penalty. Enter the total number of returns that were filed late.
The total CIS amounts you should have deducted from subcontractors in each month. Leave at £0 if nil return is toggled on.
Appeal grounds are reasonable: first default. A clear reasonable-excuse letter (illness, bereavement, software failure, or genuinely not knowing a return was due because no subcontractors were paid) is worth filing. Success is not guaranteed but HMRC's own guidance acknowledges first-default discretion.
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How CIS300 late-filing penalties work
Every contractor registered under CIS must file a CIS300 monthly return by the 19th of the month following the tax month it covers. If you made no payments to subcontractors, you must still file a nil return by that date. A late return, whether nil or not, triggers an automatic fixed penalty that escalates the longer the return remains outstanding.
The penalty ladder is: £100 from day one, an additional £200 at two months (£300 in total), then at six months the greater of £300 or 5% of the CIS deductions that were due on that return, and the same again at 12 months. For a nil return, the 5% element is always £0 because no CIS deductions were due, so the maximum fixed penalty per nil return is £900 if it remains outstanding for a full year.
Penalties stack per return. Three months of late returns each attract their own penalty independently. A contractor who misses three consecutive months and files nothing will face three separate sets of penalties, not one combined charge. This is why even short gaps can accumulate quickly.
There is an important relief for new contractors. If you are filing CIS monthly returns for the first time and earlier returns are also late, HMRC caps the total of the £100 and £200 fixed penalties across those first returns at £3,000 (set out in HMRC guidance CISR65080). During that first-filing period the £300 minimum on the 6 and 12 month penalties also falls away, so those penalties can be as low as 5% of the deductions due, or nil for a nil return. The cap covers only the fixed £100 and £200 penalties; any 6 and 12 month tax-geared penalties are charged on top and are not capped. Toggle the new-contractor option to apply this treatment.
The 12-month tier includes a further band for deliberate and concealed withholding: HMRC can charge the greater of 100% of the CIS deductions due or £3,000. This tool does not assume deliberate withholding; if you believe HMRC is applying that charge, take specialist advice immediately.
Worked examples
Three nil returns, each 3 months late, first default
A sole-trader contractor had no subcontractors for three months and did not realise nil returns were still required. Each return was filed three months late. No CIS deductions were due.
- perReturn: £100 (day 1) + £200 (2 months) = £300 (no tax-geared element on nil returns at 3 months)
- total: 3 × £300 = £900
- appeal: Strong grounds: first default and nil returns. HMRC regularly cancels or reduces these penalties on appeal.
Two returns, 7 months late, £2,000 CIS deductions each
A contractor was under investigation and delayed filing for seven months. Each return carried £2,000 of CIS deductions due. Not the first default.
- perReturn: £100 + £200 + max(£300, 5% of £2,000 = £100) = £100 + £200 + £300 = £600 (fixed floor applies because £100 < £300)
- total: 2 × £600 = £1,200
- appeal: Limited grounds. No first default and non-nil returns. A specialist can assess whether any procedural defects apply.
New contractor, 20 nil returns each 2 months late (cap applies)
A contractor registered but never realised nil returns were due, then filed 20 outstanding nil monthly returns at once, each already 2 months late. These are their first ever CIS300 returns.
- perReturn: £100 (day 1) + £200 (2 months) = £300 fixed per return
- total: Uncapped fixed penalties: 20 × £300 = £6,000, capped at £3,000 for a new contractor. No 6 or 12 month penalties apply at 2 months late. Total = £3,000.
- appeal: Strong grounds: first default, nil returns and the new-contractor cap. HMRC frequently reduces these further on appeal.
Frequently asked questions
Do I have to file a CIS300 if I made no payments to subcontractors?
Yes. A nil return must be filed by the 19th of the following month even if you made no payments to subcontractors in that period. Failing to file attracts the same £100 day-one penalty as a non-nil return. You can contact HMRC to be removed from the monthly filing obligation if you expect to have no subcontractors for an extended period, but this requires advance notification.
I have never filed a CIS return before. Is my penalty capped?
Possibly. HMRC operates a new-contractor cap. If you are filing CIS monthly returns for the first time and several earlier returns are also late, the total of the £100 and £200 fixed penalties across those first returns is capped at £3,000 (HMRC guidance CISR65080). A new contractor here means someone who has never filed a CIS300 monthly return before. During that first-filing period the £300 minimum on the 6 and 12 month penalties also does not apply, so those penalties are just 5% of the deductions due, or nil for a nil return. The cap covers only the fixed penalties; any 6 and 12 month tax-geared penalties are added on top and are not capped. Toggle the new-contractor option in the calculator to apply this.
Can I appeal a CIS late-filing penalty?
Yes. You can appeal any fixed CIS penalty if you have a reasonable excuse. HMRC accepts appeals within 30 days of the penalty notice, but late appeals can be considered in appropriate circumstances. Common reasonable excuses include serious illness, bereavement of a close family member, software failure, or a genuine and reasonable misunderstanding of the filing obligation. A history of compliance strengthens an appeal.
What is the nil-return penalty argument?
Where a return is nil (no CIS deductions were due), the penalty is the same fixed amount as a non-nil return, but there is no underlying tax at risk. Many tax professionals argue this is disproportionate, and HMRC's First-tier Tribunal has accepted disproportionality as a factor in penalty appeals in certain circumstances. Nil-return late penalties, especially on a first default, are among the most frequently reduced or cancelled on appeal.
What counts as a reasonable excuse?
HMRC's guidance (CH160000 series) lists: serious or life-threatening illness, death of a close relative, fire, flood or other natural disaster affecting your records, and postal delays outside your control. Lack of awareness of the obligation is generally not accepted unless you took reasonable steps to find out. If you relied on an agent who failed to file, the excuse may rest on the agent's conduct rather than your own.
How do I appeal a CIS penalty?
Write to HMRC within 30 days of the penalty notice, or use HMRC's online services. Your letter should state the return period, the penalty reference, the specific reasonable excuse and the date the excuse arose and ended. If HMRC rejects the appeal, you can request a review or appeal directly to the First-tier Tribunal (Tax Chamber). Specialist representation is advisable for penalties above £500 or where a deliberate-withholding charge has been raised.
Can HMRC charge more than the fixed penalty amounts?
Yes, at the 12-month stage. Where HMRC determines that a failure was deliberate, or deliberate and concealed, the charge rises to the greater of 100% of the CIS deductions due or £3,000 per return. This tool does not assume deliberate withholding. If you have received a notice citing deliberate withholding, take specialist advice before responding.
Will the penalty show on a compliance record?
Late-filing defaults are recorded on your compliance record and can affect your ability to hold or apply for Gross Payment Status. HMRC's annual Tax Treatment Qualification Test considers compliance history. If you currently hold GPS, an upheld penalty for a late return may trigger a review of your status.
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