Received 2 1099-R forms dated 2018 related to excess 401(k) deferral contributions mad in 2017. Total excess deferrals $505.50. The1099-R reported amounts are reported as $83.50 under dist. code 8 on one 1099-R and $422.00 dist. code P on the other 1099-R.
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.
You can check the status of the amended return here, but allow 3 weeks after mailing.