You receive your bills on the fifth working day of the following month by email. Alternatively, you can also view them in my yallo under "Bills and Usage".
If you have not received an invoice and have the "Invoice by Email" option enabled, please also check your spam folder. With some email providers, the invoice might occasionally end up there.
If you have selected the option "Paper bills" in my yallo (charge applicable), you will receive your bills around the middle of the month. If the total amount of your invoice is less than CHF 15.00, you will not receive an invoice and the amount will automatically be carried over to the next invoice.
If you would like to switch from paper bills to the free version sent by email, you can change this in my yallo. You can learn how that works here.