We have a number of self-assessment forms that will help you decide if your proposal needs planning permission.
If you want to be certain that your proposal does not require planning permission, you should apply for a 'Lawful Development Certificate' (LDC).
It is not compulsory to have an LDC but Coventry City Council will no longer provide written advice on whether a proposal requires planning permission. So, if it is important for you to have that clarification, you should make a formal application.
For further information on making an application for LDCs, please look at the national planning portal advice.