The Government Gateway will automatically issue you with an Activation Code for each online service that requires one. The code will be issued within 2 days of you completing your enrolment. It will be sent to the address you give for that specific service.
It can take up to 5 days for you to receive the Activation Code letter or up to 21 days if you live abroad.
You must activate the service within 28 days of the date shown on the letter you receive. If you don't, the code will expire and you'll have to request a new one.
Please note: You don't need an Activation Code to submit VAT Returns, Notification of Vehicle Arrivals or Reverse Charge Sales List declarations. These services are automatically activated.