If you have to pay more medicare payments due to increased income they use the 2017 return AGI for the 2019 cost not the 2018 ... they use 2018 for the 2020 ... so you don't need to estimate anything ... you will have a complete return to use in time for the change. 

2018 form 1040ES forms are included in the 2017 tax program, 2019 in the 2018 program and so forth.

<a rel="nofollow" target="_blank" href="https://secure.ssa.gov/poms.nsf/lnx/0601101031">https://secure.ssa.gov/poms.nsf/lnx/0601101031</a>

MAGI for 2018 is substantially less than MAGI for 2017, so i plan to appeal the IRMMA based on estimated income for 2018 (which is 1 month to 12/31/18).  I only have 60 days to appeal the IRMMA assessment based on 2017 MAGI, which is too high for 2018 income and will penalize me in 2019.