Conn. Gen. Stat. § 12-408g

(b) For a taxable sale occurring on or after December 1, 2018, but on or before December 31, 2019, if a marketplace facilitator incurs liability for failure to collect the tax due under this chapter on a taxable sale, the commissioner shall limit such liability in accordance with the provisions of subdivision (1) of subsection (c) of this section if such facilitator can show to the satisfaction of the Commissioner of Revenue Services that (1) such facilitator and the marketplace seller are not affiliated persons, as described in subparagraph (C) of subdivision (15) of subsection (a) of section 12-407 , (2) the failure to collect sales tax due was not due to an error in sourcing the sale, and (3) such sale occurred on or before December 31, 2019. The commissioner shall prescribe the form and manner in which a marketplace facilitator may request the relief in this subsection.

(c) (1) The commissioner shall limit the liability of a marketplace facilitator who the commissioner deems to have satisfied the provisions of subdivisions (1) to (3), inclusive, of subsection (b) of this section by reducing the total amount of tax due under this chapter on taxable sales facilitated by such facilitator and sourced to this state by five per cent, reducing the interest due by a corresponding amount and waiving any associated penalties.

(2) The commissioner may limit the liability of a marketplace seller who incurs liability for tax due under this chapter on a taxable sale that was made through a marketplace facilitator to the same extent as provided under subdivision (1) of this subsection, provided the commissioner deems the provisions of subdivisions (1) to (3), inclusive, of subsection (b) of this section to be satisfied.