If you are paid monthly, you should check your Universal Credit payment statement as soon as possible to see if your award is less than expected. If it is, check the earnings information on the statement.
If it looks like two of your monthly salary payments have been used to calculate the award (or a salary payment has been reported late or otherwise in the wrong assessment period), you should contact the DWP as soon as possible and ask them to re-allocate one of the salary payments to a different assessment period.
You may need to provide additional information or evidence. The DWP say that in most cases they will be able to action this quickly and change the award in time for the correct payment to be made on the usual Universal Credit payment date. But it is important to contact them quickly and not wait until the Universal Credit payment is made because that will lead to delays putting the payment right. Some cases which are more complex may take longer for DWP to adjust.
The quickest way to contact the DWP on this issue is through your Universal Credit (UC) Journal, although you can also telephone the UC Helpline on 0800 328 5644.