Where you are on UC and you sell your house with the intention of buying another, then any capital you have from the sale of your old house is disregarded for up to six months.
In addition, if you have money that is specifically intended to be used for making essential repairs or alterations to premises occupied or intended to be occupied as your home then that is also disregarded for 6 months as well.
You my wish to let them know that you will be selling your home and that the proceeds of the sale will be passing through your bank account and that some of the money will then be used for making alterations to the property so that it is suitable for you.
They will then disregard this capital for at least 6 months and longer if the alterations to your new home take longer than that.
You can read all the details here in the the detailed rules about capital in the DWP ADM Chapter H2 (Capital Disregards) from the gov.uk website:
https://assets.publishing.service.gov.uk/media/654111fb1f1a60000d360b54/admh2.pdf
The relevant parts are on pages 24 and 25
Amount to be used to purchase premises
H2119 Where a person has received an amount within the past 6 months which is to be used to purchase premises that the person intend to occupy as their home, that amount can be disregarded from the calculation of that person’s capital where it
- is attributable to the proceeds of the sale of premises formerly occupied as their home or
- has been deposited with a housing association (see H2045) or
- is a grant made to the person for the sole purpose of purchasing a home [UC Regs, Sch 10, para 13]
Amount for repairs
H2123 Where, in the past 6 months, a person has acquired a sum of money by way of a loan, grant or otherwise which is to be used for making essential repairs or alterations to premises occupied or intended to be occupied as the person’s home, that amount can be disregarded from the calculation of that person’s capital but only where it is used for that purpose. [UC Regs, Sch 10, para 15]
By the way, the references in square brackets are to The Universal Credit Regulations 2013, Schedule 10