The following table summarizes the cumulative amount of contractual payments made as of December 31, 2017 for our rigs under construction and estimated timing of our remaining contractual payments (in millions):



	Cumulative Paid⁽¹⁾		2018 and 2019		2020 and 2021		Thereafter		Total⁽²⁾
ENSCO 123⁽³⁾	$	67.1	$	218.3	$	—	$	—	$	285.4
ENSCO DS-14⁽⁴⁾	—		15.0		165.0		—		180.0
ENSCO DS-13⁽⁴⁾	—		83.9		—		—		83.9
	$	67.1	$	317.2	$	165.0	$	—	$	549.3


⁽¹⁾	Cumulative paid represents the aggregate amount of contractual payments made from commencement of the construction agreement through December 31, 2017. Contractual payments made by Atwood prior to the Merger for ENSCO DS-13 (formerly Atwood Admiral) and ENSCO DS-14 (formerly Atwood Archer) are excluded.


⁽²⁾	Total commitments are based on fixed-price shipyard construction contracts, exclusive of costs associated with commissioning, systems integration testing, project management, holding costs and interest.


⁽³⁾	In January 2018, we paid $207.4 million of the $218.3 million unpaid balance. The remaining $10.9 million is due upon delivery. The $207.4 million milestone payment was invoiced and included in accounts payable - trade as of December 31, 2017 on our consolidated balance sheet.

⁽⁴⁾

The remaining milestone payments for ENSCO DS-13 and ENSCO DS-14 bear interest at a rate of 4.5% per annum, which accrues during the holding period until delivery. Delivery is scheduled for September 2019 and June 2020 for ENSCO DS-13 and ENSCO DS-14, respectively. Upon delivery, the remaining milestone payments and accrued interest thereon may be financed through a promissory note with the shipyard for each rig. The promissory notes will bear interest at a rate of 5% per annum with a maturity date of December 31, 2022 and will be secured by a mortgage on each respective rig. The remaining milestone payments for ENSCO DS-13 and ENSCO DS-14 are included in the table above in the period in which we expect to take delivery of the rig. However, we may elect to execute the promissory notes and defer payment until December 2022.