Before you start — Part A, Part B, and when COP3 is needed
COP3 is not the application itself — it's the evidence that supports one. Getting the two-part split right, and understanding what Part B is (and isn't) asking, saves a wasted trip to the GP.
What COP3 actually proves
COP3 exists to show the Court that the person named ('P' throughout Court of Protection paperwork) genuinely lacks capacity for the SPECIFIC decision the application is about — not capacity in general.
It is always filed together with the main COP1 application form, never on its own.
The two-part split
Part A (Sections 1-3) is completed by you — the applicant, or your solicitor. It names the person, states what decision needs to be made, and explains why an order is necessary.
Part B (Sections 4-7) can only be completed by an independent professional with relevant expertise — gov.uk calls this an 'appropriate assessor', giving medical practitioners and social care professionals as examples. You hand the form to them once Part A is finished; they complete the rest and return it to you.
When you actually need this form
COP3 supports any Court of Protection application where lack of capacity is the reason the Court needs to get involved — most commonly a Property & Financial Affairs deputyship (alongside COP1, COP1A and COP4), but also welfare applications and one-off orders for a single decision.
If the person already has a valid, registered Lasting Power of Attorney (or a registered Enduring Power of Attorney made before October 2007), you don't need this route — the attorney already has authority. COP3/COP1 is the fallback for when no valid power of attorney exists.
What Part B is not
Part B isn't a diagnosis form and doesn't ask the assessor to certify a medical condition on its own terms. Sections 6.1-6.8 ask the assessor to work through the Mental Capacity Act's own test, decision by decision — whether the person can understand, retain, use/weigh the relevant information, and communicate a decision, and only then whether an impairment of the mind or brain explains why not.
A letter simply stating 'this patient has dementia and lacks capacity' is not the same thing, and the Court will not accept it in place of a properly completed COP3.
COP3 is not the application itself — it's the evidence that supports one. Getting the two-part split right, and understanding what Part B is (and isn't) asking, saves a wasted trip to the GP.