When do you change transmission fluid in a 2005 VW Beetle?

Assuming you are talking about an automatic trani, You have to take the driver wheel off and the plastic surrounding the fender so you can see. The oil supposed to last forever because it is synthetic and the warranty only last for a few years, having said that, if you are out of warranty, what you could do is put your car up somehow on four stands, the car has to be level, drain the oil from the trani case, there is a plug in it, then you must and I repeat, you must not spill any of the oil outside the container you are using to collect the used oil. After the oil has drained, it is recommended you take the trani oil off so you can replaced the trani oil filter and to check for metal shavings. Then assuming you do all that, put the new filter and gasket back on and tight the screws to the touch + a 15% more. Then locate the oil spout right above the trani oil pan towards the front of the car, it is about 2 inches long and it is sealed, I meant it has some kind of plastic ring generally color red, you have to brake it, once you do that you also have to have a funnel and a hose small enough to fit that spout, you have to route the hose somehow in between the engine and the radiator. Now you must measure the oil taken out and and pour the exact amount in with out spilling any out because, believe me if it is less or a bit more, your trani will act up. The oil you can get only at the dealer for about 25 bucks a quart, also synthetic pour it in, put the cover back in and presto. It sound like a lot of work, but...... it is! I hope this helps, and by the way. I will not be responsible for any omissions as I am not a mechanic, not responsible for anything that may go wrong with your vehicle. This is what I've done to my daughters vehicle and it is working fine