Mae CaThEM yn cadw’r cyfrifoldeb am gasglu a rheoli CTIC, ac fel rhan o’r broses weithredu, drafftiwyd a chyhoeddwyd Cytundeb Lefel Gwasanaeth rhwng Llywodraeth Cymru a CaThEM yn gynharach eleni. Mae’r Cytundeb Lefel Gwasanaeth yn amlinellu’r gofynion, y graddfeydd amser a’r mesurau perfformiad ar gyfer gweithredu CTIC, a fydd yn sicrhau y rhoddir gwasanaeth o ansawdd cyson i drethdalwyr yng Nghymru a galluogi CaThEM a Llywodraeth Cymru i ddiwallu eu cyfrifoldebau priodol yn ymwneud â gweithredu treth incwm Cymru.
HMRC retains responsibility for the collection and management of WRIT, and as part of the implementation process a Service Level Agreement (SLA) between Welsh Government and HMRC was drafted and published earlier this year. The SLA sets out the requirements, timescales and performance measures for the operation of WRIT, which will ensure a consistent quality of service to Welsh taxpayers and allow HMRC and the Welsh Government to meet their respective responsibilities in respect of operating Welsh income tax.