Prif ddiben y Gyllideb Atodol hon yw alinio strwythurau cyllidebol 2013-14 â’r newidiadau ym mhortffolios a chyfrifoldebau’r Gweinidogion a gyhoeddwyd gan Lywodraeth Cymru ym mis Mawrth, a dangos y newidiadau cyllidebol ers Cyllideb Derfynol 2013-14 a gyhoeddwyd gan Lywodraeth Cymru ym mis Tachwedd. Mae’n nodi hefyd nifer o ddyraniadau o’n cronfeydd wrth gefn, trosglwyddiadau rhwng Adrannau Llywodraeth Cymru a throsglwyddiadau ag Adrannau Llywodraeth y DU. Mae hefyd yn cynnwys rhagolygon diwygiedig ar gyfer Gwariant a Reolir yn Flynyddol.
The main purpose of this Supplementary Budget is to align the 2013-14 budget structures with the changes to the Ministerial portfolios and responsibilities announced by the Welsh Government in March, and to reflect the budgetary changes since the Final Budget 2013-14 published by the Welsh Government in November.  It also sets out a number of allocations from our reserves, transfers between Welsh Government Departments, transfers with UK Government Departments and includes revised Annually Managed Expenditure forecasts.