As PP have said there is a claimant commitment.
It is possible that you may have to look for more work even if you are working again the moment "in work conditionality". Turn2us is a charity and has the following detail
"In-work conditionality
You might face conditionality requirements even though you are already in work. Your conditionality requirements depend on how much you are earning and whether your wages are over your earnings threshold.
If you are earning below your threshold you will be expected to make efforts to increase your income. The DWP suggest that this may include increasing the hours you work, finding additional work or finding a new job with a higher income.
The threshold is based on what you would earn if you worked for 35 hours a week at the National Minimum Wage. Though if you have caring responsibilities your threshold may be lower than this. If you are claiming as a couple, the DWP will look at whether you are earning above your threshold as a couple.
If you are single and earning over your earnings threshold, or you are a couple and earning over your joint earnings threshold, you will be subject to no work-related requirements.
If you are single and earning less than your earnings threshold but more than £338 per month, you will be subject to all work-related requirements, except for looking for work. You will still have to be ready to take up more work, to do the things your job coach asks you to and to go to work-focused interviews.
If you are a couple and earning less than your joint earnings threshold but more than £541 per month, you will be subject to all work-related requirements, except for looking for work. You will still have to be ready to take up more work, to do the things your job coach asks you to and to go to work-focused interviews.
If you are single and earning less than £338 per month, or you are a couple and earning less than £541 per month, you will be subject to all work-related requirements. The amount of time you are expected to spend on looking for and preparing for work will depend on how much you are working and if you have caring responsibilities."
www.turn2us.org.uk/Benefit-guides/Universal-Credit/Claimant-Commitment-Conditionality