CT-1065/CT-1120SI ES must be electronically paid to avoid a 10% failure to comply penalty for the amount of the payment.  The 2019 and 2020 voucher (coupon) looks like every other ES coupon on Proseries.  The only mention of a penalty for non-electronic payment is practically hidden within a paragraph on the Smart Worksheet on a 2nd page of only the 1st coupon [ES 1].  Perhaps a warning watermark on all 4 ES coupons is in order?