Driving across Austria

The Italian motorway has tolls up to Brenner pass, paid in cash. The Austrian motorway from Brenner to Innsbruck-Süd has its own toll but the vignette is not needed as you have to pay in cash anyway. If you do not leave the motorway at Innsbruck-Süd you need a vignette (frequent checks and stinging fines) - so you likely need one. You can purchase vignettes at the last few motorway stations in Italy or at Brenner pass. Vignettes come in three durations: ten days, two months, one year. The starting date has to be punched on the vignette and the vignette has to be glued on the car screen. Unpunched and unglued vignettes are not valid.

The ten day vignette is valid for the punched day and nine following days. For example, a vignette punched on Aug. 10th is valid till Aug. 19th included. From Aug. 20th you would need another vignette (or consider the two months one).

Thanks for your very detailed response! That answers my question completely!

as above, plus

http://www.asfinag.at/toll/toll-sticker/

10 day sticker is €8,90

you're question reads as though this is just a quick dash across austria, if so which german border crossing were you planning on using? If the Seefeld to Mittenwald road crossing at Scharnitz the austrian autobahn section would only be about 15 minutes and only saves about 10 minutes (outside the commuter peak hours). Although the non-autobahn alternative uses the Innsbruck inner ring road it isn't too difficult (outside the commuter peak hours)

Are you renting a car in Italy and returning it in Germany? If so, I'd like to caution you about the very hefty fee you will be charged for returning the car in another country. If you need a car in Italy and Germany, but are just quickly driving through Austria, you might consider taking the train from Italy to Germany instead.