There is no time limit to make a superseding decision from the date DLA commenced. Nor is there any time limit to revise any HB decision made during the period covered by arrears of DLA when it is first awarded (usually takes a while to process so quite likely an HB decision would have been made in between the date of the DLA claim and the date of the decision awarding DLA).
What’s not so clear is how you can revise any subsequent HB decisions made after the claimant started receiving DLA but before you found out about it. A strict interpretation of the D&A Regs would say those more recent decisions cannot be revised, so you add the DLA for a short period from a date in 2016, then take it out, then start again from 2020. Many authorities would say life is too short to mess about like that, and if you are going back to 2016 at all then you are going back to 2016 with no strings.
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