Migration offices are available in All formal border crossing checkpoints. You can process your visa application upon arrival in all Tanzania border crossings !

Fellow travellers advice on visa can be obtained from here https://www.tripadvisor.com/ShowTopic... 

Additional info are obtained from the government migration website 

Also Tz Revenue Auothority TRA offices are available at all official border cross ings ,this means that if you are travelling with certain business goods& products to/from Tanzania you will be required to pay for tax and the TRA offices are there to process the payments !

 A  few of border crossings are ;

  1. Namanga Kenya/Tanzania crossing via Nairobi-Arusha  
  2. Horohoro Kenya/Tanzania crossing via Mombasa-Tanga