Hi @Christof Gardet, is this deal for renting/flipping?
I have a 5 bdr in Henrico County that the county states is 3 bdr. Here's the deal, the number of bedrooms listed with the county doesn't usually effect what people are willing to pay for the property in rent or purchase price as long as it's a true 3 bedroom. That said, the appraisal is going to give you a value based on 2 bedrooms, so it's important to be careful as it can effect both your lending and (if it's a flip) your buyer's lending. If the appraised value comes in below the agreed on purchase price, your buyer usually will have to make up the difference on a conventional mortgage, which may decrease the likelihood to close.
That said, the assessor's office can always re-assess the number of bedrooms in the property, permits or not. You can call their office to find out more and what can be done. Henrico County is easy to work with, not sure about Richmond City