How am I able to file for the years 2015, 2016, 2017 & 2018?

[davidsolo-bell-n]

I had help with an agency to file for 2019, 2020 & 2021.  He informed me that I could also file the missing previous 4 years online but it won't let me

[TurboTaxGinette]

1-Netfile is only available for the previous 5 years, which are 2018 to 2022, through the Canada Revenue Agency (CRA) therefore, 2017 and older will have to be sent in by mail. Please use this link for the Mailing address for CRA.

2-You can use TurboTax software starting in 2016 File past years' taxes but you will need to get older paper returns from the Canada Revenue Agency (CRA) Tax packages for all years. 

For more information, please see this Canada Revenue Agency link: File your taxes online: Understand NETFILE. 

Thank you for choosing TurboTax.