Please pay the interim individual income tax by the end of Nov., it's around half amount of the March return.
Around 14bil. sole-proprietors are need to pay this time, but if it's less than 30% of the last March, you can file your approx. income this time, and reduce your interim tax to pay or skip it this time.
For payment, you can pay it by a credit card and pay by partially if it's more than 10mil.won.
More details, please send me an email to firstname.lastname@example.org