The three-step manual estimate
Step 1: estimate the qualifying base. Not your R&D budget: the apportioned staff costs, 65% of unconnected bought-in work, consumables, software, data and cloud, less overseas exclusions. Most estimates are wrong here, not at the rate. Work from qualifying costs.
Step 2: pick the route. Loss-making, R&D-intensive SME through all three ERIS gates: ERIS. Everyone else: the merged scheme. The gates are on ERIS explained.
Step 3: apply the arithmetic. The current rates, the after-tax netting and worked examples for both routes are maintained in one place, how much you can claim. That way this page never carries a second copy that can drift out of date.
Why we will not launch it half-checked
A calculator is the most quoted, screenshotted, decision-driving page an advisory site has, and the least able to carry nuance. Ours will launch when its figures are signed off, and it will still say what this page says. The rate is public, your base is not, and the way to know where you stand is a short, honest conversation.