WTC vs UC?
I have a client with learning disabilities who works 16 hours a week. This job was for the first few years supported, though he can now work without support albeit is always closely supervised. He was entitled to DLA lowest rate care, which meant he was entitled to WTC.
He came up for PIP conversion and a decision was made in February that he was not entitled to any rate of PIP. That decision is under appeal and I am confident of winning it. The appeal will not be listed for hearing before 13/06/18, which is the date that this area goes UC full service.
Because he was no longer entitled to a disabled worker element his WTC ended. If he wins his PIP appeal can the decision ending his WTC be changed and the WTC award reinstated, or does it count as a new claim in which case he will have to claim UC?
This client will be worse off financially under UC, while any work search requirements are likely to have a detrimental effect on his health and that of his appointee.
This situation would usually involve a new claim, which could be backdated more than 31 days under Reg 8 of the Tax Credits (Claims & Notifications) Regs if the PIP appeal is determined in the claimant’s favour. However, as you say a new claim is not possible after the UC full service date, except for claimants with 3 or more children or claimant or partner over PC age.
But he may have qualified, and can continue to qualify, as a disabled worker under another route, under Case A, B, E or F (for example, if he was getting ESA for at least 28 weeks in the six months before starting work). If so, he remained entitled as a disabled worker under case G, as long as there is not a break in his claim of more than 56 days, and he still has a disability as listed in Schedule 1 (CPAG handbook p.1663). Case B also includes a disability premium in housing benefit, so even if this has now ended, he can continue to qualify because he was getting it ‘at some earlier time’. See CPAG handbook p1429 last bullet point and footnotes to TC956 and PW v HMRC  UKUT 12. If this applies, then a mandatory reconsideration of the decision that he was no longer entitled to WTC would be worthwhile.
Alternatively, the provision that allows renewal claims for tax credits in The Welfare Reform Act 2012 (Commencement No. 23 and Transitional and Transitory Provisions) Order 2015 Article 7, is worded in a way which arguably could apply to your client:
(6) Paragraph (1) does not apply to a claim for a tax credit where a person is or was, or persons are or were, entitled to child tax credit or working tax credit in respect of a tax year and that person or those persons makes or make (or is or are treated as making) a claim for that tax credit for the next tax year.
Let us know how you get on.