Two thirds of Britons enjoy the process of buying and selling on online marketplaces, with the average adult trading 21 items so far this year, according to a survey.

The poll, which involved 2,000 adults, found that fashion items, hobby products, and home and gardenware were the most frequently bought and sold items.

Interestingly, one fifth of respondents consider selling second-hand goods online as their 'side hustle', with some earning more than £400 per month. Nearly one in 10 have even turned selling on online marketplaces into their full-time occupation.

For 80% of sellers, maintaining a high overall rating on their profile is crucial. To achieve this, 48% ensure swift package delivery, while 43% commit to responding to queries within an hour.

Sellers are aware that nearly half of buyers are put off by poor reviews, as 40% won't proceed with a purchase until they've scrutinised them.

Neill O'Sullivan, managing director of parcels and mails at Post Office, which commissioned the study, commented: "It's incredible to see how many people are not only decluttering through online marketplaces but also turning it into a significant income stream.

"Maintaining a high seller rating has become crucial, with quick delivery and prompt communication being the key to happy customers."

He added: "In a world where next-day delivery is expected and customers want to see exactly where their parcels are along the way, we know the importance of ensuring packages are tracked and arrive safely.

"Now even smaller sellers can offer this kind of service if they use the right delivery carrier."

The surge in marketplace popularity could be attributed to the wide range of products on offer (62%), with 58% citing the convenience of shopping from home as a key factor.

Almost half (48%) appreciate the ease of price comparison, while 39% relish the chance to sell unwanted items for extra cash. However, high shipping costs have deterred 53% from purchasing from an online seller.

Alison De Lara, founder of Mamma Duck Company, who has been retailing her sought-after wooden ducks online since 2013, shared: "While being an online seller has been brilliant at allowing me to grow my business and build loyal, returning customers, it comes with its challenges such as ensuring items get to them on time and securely."

"For me, affordable delivery options, convenient drop-off locations, and reliable tracking are important aspects which make sending items a positive experience."

"Tracking, in particular, gives my customers peace of mind and being able to offer delivery options that suit their budget and time scale has absolutely been key in boosting my customer experience," she adds.

Neill further commented:"With Christmas on the horizon, shoppers are more likely to spend with sellers who can offer a choice of delivery options and provide tracking, matching the service from big brands."

"A variety of delivery carriers means online sellers can make the most of the Christmas rush, without the stress, as Postmasters can advise on the most suitable posting options."