The code 8 is for taxable earning received in 2018 that are reported on your 2018 tax return.
The code P is the return of 2017 excess that must be include as 2017 wages on an amended 2017 tax return.
Amended returns can only be mailed. It is suggested that it be mailed certified with return receipt (or other tracking service) to verify that the IRS receives it.
https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed
https://ttlc.intuit.com/replies/3288565
You can check the status of the amended return here, but allow 3 weeks after mailing.
https://www.irs.gov/filing/individuals/amended-returns-form-1040-x-/wheres-my-amended-return-1
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
