The charity's 2022 Challenge is encouraging people to donate their unwanted items to its shops, rather than throwing them away.
The aim is to gather 2.2million bags of donations by the end of the year, with every one being turned into more support for older people.
Anna Taylor, manager at the Shoreham shop, said: "If you’re having a spring clean and a sort out, please try to bring at least two bags, or more if you have them, of unwanted, items to your local Age UK shop.
"We accept clothes, shoes, books, accessories, toys and homeware, although please make sure that these are good quality and not damaged or torn.
"Not only will you be decluttering your home and helping us raise funds to support older people when they need it most, you will also be helping the planet by recycling and reducing waste.
"Donations can be maximised by signing up to gift aid. That extra money doesn't cost a penny and helps us raise more valuable funds for people in later life."
The shops in Wallace Parade and Chapel Road, Worthing, are also keen to receive donations.
Jackie, the Chapel Road shop manager, said she would particularly welcome bric-a-brac and books.
She explained: "We are a little bit different. We are a pop-up shop, so everything is sold at a discount price.
We have plenty of clothes, as everything in our shop has been in two of our other shops already. You can get some lovely stuff and most are just £1."
Funds raised will go towards services such as Age UK’s free national advice line and its telephone friendship services, which are still in huge demand from older people who have no one else to turn to.