R&D tax credit calculator.

The test is whether you were trying to resolve a scientific or technological uncertainty that a competent professional in the field could not readily work out. It is not about novelty to you, and it is not about whether the project succeeded. Building a website with familiar tools is not R&D even if it is hard work; making software do something nobody had established was possible may well be. The uncertainty has to be technological, which is why commercial or design uncertainty does not count.

Staff costs for people directly working on the R&D, including a proportion of salary, employer's NI and pension. Consumables genuinely used up. Software, and data and cloud computing costs used for the R&D. Payments to clinical trial volunteers. Subcontracted R&D and externally provided workers are included but restricted, and the rules on who can claim when work is contracted out changed under the merged scheme — broadly the company that decided to do the R&D claims it, not the one carrying it out. Capital costs, rent and rates are excluded.

Under the merged scheme the credit is 20% of qualifying spend, but the credit is itself taxable, so at a 25% corporation tax rate it is worth about 15% net. That is the figure to budget on, and it is the detail most calculators skip. Under ERIS a loss-making R&D-intensive SME gets an 86% additional deduction plus a 14.5% payable credit on the surrenderable loss, which is worth substantially more.

Enhanced R&D Intensive Support is for loss-making SMEs whose qualifying R&D is at least 30% of total expenditure. The intensity test is measured across connected companies, which is what catches groups out — a research company sitting inside a group with a large trading subsidiary often fails the test on its own numbers being diluted by the group's.

Often, yes, and missing it is fatal to the claim. You must submit a claim notification form within 6 months of the end of the period of account if you are claiming for the first time, or if your last claim was made more than three years before the last date of the claim notification period. Separately, every claim needs an additional information form submitted before the Company Tax Return. A claim without it is simply removed.

Two years from the end of the accounting period. So a company with a 31 March year end has until 31 March two years later to claim for that year. If you have never claimed and think you should have, that window is the first thing to check — but watch the notification rule above, which can bite before the two years are up.

Not necessarily, but it changes the route and the value. Notified state aid received for a project can push that project's expenditure out of the more generous SME treatment, and subsidised expenditure rules apply. It is worth taking advice before accepting a grant on a project you expect to claim for, because the interaction is easier to plan than to unpick.

Because the relief was heavily abused. A wave of firms sold claims on contingent fees, often to businesses doing no R&D at all, and HMRC's compliance response has been blunt — volume checks, and a willingness to reject claims that are not clearly evidenced. A well-documented claim is still perfectly safe. One assembled from a template by somebody who never asked a technical question is not.