The investor tax relief on interest is given against the rent at your marginal rate, so for a 20 or 41% taxpayer it's worth 20 or 41% of the interest. TRS for OO is at 20% only so for a 41% taxpayer investor interest relief is worth more than TRS. There are also limits on TRS amounts but no limit on investor interest. Be aware tho that to claim investor interest relief the property must ber registered with the PRTB