For employed claimants
The DWP are sent information about the claimant's earnings by HMRC and therefore any wage changes will be picked up. If their earnings drop, then their UC award will generally increase. If their earnings increase, then their UC award will usually drop.
It is what is paid in each Monthly Assessment Period (MAP) that counts - even if this includes earnings in respect of past (or future) periods.
A drop in earnings could affect the conditionality group the claimant is in. In which case they will need to agree a new claimant commitment and ensure they complete any tasks required.
For self-employed claimants
The claimant has to report their earnings and allowable expenses at the end of each MAP, so any changes in income will be picked up.
If the claimant makes a loss in any one MAP this can be carried forward and offset against future income.
However, they may be affected by the Minimum Income Floor, which means the DWP may take a higher income figure into account when working out their UC award than they actually received.
Transitional Element
If they have a Transitional Element in their UC award, and their earnings drop, then they may lose this Element.
Surplus Earnings
If they receive a large payment of earnings, and their UC award drops to nil, then they may be affected by the surplus earnings rules.