EBU Single Rulebook Q&A 28 July 2016 2016_2849 Gross-up calls on Tier 2

Should gross-up cases on Tier 2 be allowed only in relation to coupon withholding tax (and not principal)? Article 20(2) of the RTS for Own Funds requirements for institutions includes in the forms of incentive to redeem AT1 and Tier 2 a call date combined with an increase in the credit spread and / or the redemption amount.