In reply to Kemics:
> My question is - how quickly can you get set up with this?
Varies enormously depending on your own personal circumstances, how simply you fit the eligibility criteria, how helpful you are to "them" with providing info and details, etc.
You mention WTC and HB (and presumably CTR?). Former is a claim to HMRC and depending on when you claim/notify change of circumstances, method of claiming, and how fully you provide the info they need, usually anything from 4 - 6 weeks as a minimum to months or more, but that does not necessarily mean you will get any monies in that timescale as you may have to wait till the following tax year anyway depending on your actual circumstances. The latter (HB/CTR) is processed by local councils, and again it varies alot. Locally it is 2-3 weeks weeks for simple claim, up to months for a complex one. You are in a catch 22 situation as you have limited scope to claim in advance of a change of circumstances (one month I think from memory is max for HB), and a max of one month after otherwise benefits may be affected. You can ask your local council how long it normally takes for them to process a claim and that will give you a guide. I would not bother asking HMRC though re WTC, but you could I think from memory it is possible to submit a protective claim based on current job (knowing that no monies will be paid), and notify change of circumstances after. At least you are in the system so been through basics of right to reside, habitually resident, etc, rules of eligibility, though I hasten to add that that does not mean that you will get monies any quicker after the change notified!
> Do I have to have a history of working at my new rate
No, not to submit a claim.
> or are they going to look at what ive been earning previously, or just on my new wage?
Both past and future wages will be taken into account in any benefit calculation if applicable, as will savings/assets past and present if applicable, and also importantly your partner's past and present income and savings/assets if applicable.
Presumably irrelevant as you have the official government calculator decision, but just in case you inputed wrongly as you do say part time - you do know for WTC that to be eligible in principal (amoungst other rules) if indeed you are aged 25yrs assuming single and no children that you need to work 30hrs or more? There are exception rules which of course you may meet which may allow 16 or more hours, or even the combo of 24 hrs rule? Not enough info given to tell what your circumstances actually are so sorry for assumptions.
If in any doubt as to your eligibility I strongly suggest you take further advice from the likes of a CAB or direct with HMRC and or your local council, as it could be a costly mistake if you move jobs expecting benefits to top up your income and discover after that you do not qualify.