ICAEW Principles of Taxation (ICAEW) common mistakes
ICAEW Principles of Taxation · Understand the traps and how to avoid them.
Computing income tax on the taxable income figure without first deducting the personal allowance (or applying it to the wrong income source), then carrying the wrong liability into the rest of the answer.
Candidates learn the rate bands first and treat the personal allowance as an afterthought, or they forget that the allowance is set against total income before the bands are applied. Under exam time pressure the allowance line gets skipped entirely.
What to do instead
Build a fixed pro-forma for every income tax computation: total income, less reliefs, less personal allowance, equals taxable income, then split taxable income across the basic, higher and additional rate bands in that order. Practise the pro-forma until the allowance line is automatic, and always state the allowance figure explicitly even when it is nil because income exceeds the abatement threshold.
Ignoring the personal allowance abatement for high earners and applying the full allowance whenever adjusted net income is above the basic rate limit.
The £1-for-£2 abatement and the complete withdrawal at £125,140 is a rule candidates read once and then forget; it only bites on a minority of questions, so it never becomes habitual.
What to do instead
Before every computation, compute adjusted net income (total income less gross gift aid and pension contributions) and test it against the £100,000 threshold. If it exceeds £100,000, reduce the allowance by half the excess and show the calculation as a separate line. Drill three or four abatement scenarios, including one where the allowance falls to nil, so the test becomes a reflex.
Treating an employee's taxable benefit as the cash cost to the employer, or as the amount the employee reimbursed, instead of applying the specific valuation rule for that benefit.
Benefits are a long list of separate rules (company cars by CO2 and list price, fuel by scale charge, beneficial loans by the official rate, living accommodation by annual value or cost) and candidates default to 'cost to employer' because it is the general rule for most assets.
What to do instead
Learn a benefits decision tree keyed to the asset: car (list price × CO2 percentage, with the fuel scale charge computed separately), loan (average balance × official rate less interest paid, with the £10,000 threshold), accommodation (annual value plus, if cost over £75,000, the additional rental value). For each benefit, write the rule name next to the figure so a marker can see the correct basis was used even if arithmetic slips.
Classifying a worker as self-employed or employed using only one factor such as the label in the contract, rather than weighing the case-law tests.
Candidates look for a single decisive fact and stop, whereas employment status turns on a bundle of factors: control, personal service and substitution, mutuality of obligation, financial risk, and whether the engager is 'in business'.
What to do instead
Answer status questions with a structured two-column analysis: factors pointing to employment, factors pointing to self-employment, then a conclusion. Cite the tests by name (control, substitution, MOO, risk of loss) and note that the written contract label is not decisive. Practise on short scenarios so the factor list becomes the answer structure.
Applying capital allowances at the wrong rate or to the wrong pool, for example putting a car with high emissions in the main pool or claiming the annual investment allowance on cars.
The pool structure (main pool, special rate pool, single asset pools) and the interaction of AIA, full expensing and the 100% first-year allowance for zero-emission cars is layered, and candidates memorise rates without the eligibility conditions.
What to do instead
Draw the pooling diagram from memory: main pool at 18% reducing balance, special rate pool at 6%, AIA up to £1m available for most plant and machinery but not cars, full expensing for new qualifying main-pool plant, and 100% FYA for new zero-emission cars only. Then work through a mixed additions example where every addition is allocated to a pool before any allowance is computed.
Computing a capital gain without applying the correct relief or exemption order, for example deducting the annual exempt amount before losses or before business reliefs.
The order of set-offs (current-year losses, brought-forward losses, annual exempt amount, then reliefs such as business asset disposal relief or gift relief) is procedural and easy to state in the wrong sequence when writing quickly.
What to do instead
Use a strict vertical layout: proceeds, less allowable costs, equals gain; less current-year losses; less brought-forward losses; less annual exempt amount; then apply the relevant relief to the remaining gain and state the rate. Annotate each line with the rule name. Do the same layout for every gain in a multi-disposal question so each disposal is self-contained.
Missing or misapplying the reliefs on a gift or sale at undervalue, such as gift relief or business asset disposal relief, because the candidate does not first confirm the asset qualifies.
Reliefs have qualifying conditions (trading status, personal company shareholding and voting rights, minimum holding period) and candidates jump to the relief calculation without running the conditions, or they apply relief where the asset is an investment.
What to do instead
For every relief, write the qualifying conditions first as a checklist and tick them against the scenario before computing anything. For business asset disposal relief, confirm the trading company, the 5% ordinary share capital and voting rights, and the two-year holding period. For gift relief, confirm the asset is a qualifying business asset and note that the gain is held over rather than eliminated.
Calculating corporation tax on accounting profit without adding back disallowable expenditure such as depreciation, entertaining, and non-trading loan relationship deficits, or without claiming the super-deduction or full expensing correctly.
Candidates treat the accounts profit as the tax base and adjust only for the items they happen to remember; the long list of add-backs and the capital allowances replacement of depreciation is where marks are lost.
What to do instead
Work a standard adjustment pro-forma every time: accounting profit, add back depreciation and disallowables (client entertaining, fines, capital items), deduct non-taxable income, deduct capital allowances, then apply the rate. Keep a one-page add-back checklist and rehearse it until every adjustment is considered, even if the answer is nil.
Confusing the VAT treatment of supplies, for example charging VAT on zero-rated or exempt items, or recovering input VAT on exempt or non-business expenditure.
Zero-rated and exempt both look like 'no VAT charged', but they differ on input tax recovery and on registration thresholds; candidates collapse the two categories.
What to do instead
Build a three-way table: standard-rated, zero-rated, exempt, with the output tax treatment and the input tax recovery consequence for each. Then practise a mixed-supply business computing output tax, input tax and the net payment, explicitly labelling each supply category. Remember that zero-rated supplies count toward the registration threshold while exempt supplies generally do not.
Running out of time because the candidate writes long narrative answers to computational questions and never attempts the final requirement.
The exam rewards working and method marks, but candidates over-explain early parts and then leave a whole requirement blank; a blank requirement scores zero regardless of how good the earlier prose was.
What to do instead
Allocate time per requirement before starting and stick to it. For computational parts, show figures in a column with one-line labels rather than sentences. If time is short, write the pro-forma with the method and any figures you have, because method marks are awarded for the correct structure even when the final number is wrong. Rehearse full papers under timed conditions so the pace becomes calibrated.