Does this mean that you need to "own" a taxi, or that you need to hire the services of one? That is, would you say this (despite it being a little demanding and rude) if you were on the phone to the taxi company, say?
In case it can be said of needing to hire the services of a taxi, would it really be viewed as a little demanding and rude, rather than a simple statement of fact?
Sorry, this exercise is incorrect, I've fixed it now but it may take some time to come live. Tá tacsaí uaim means I want a taxi. Teastaíonn tacsaí uaim can mean either I need a taxi or I want a taxi.