Fashion represented 27% of all eCommerce purchases in 2018 according to Australia Post's most recent Inside Australian Online Shopping report.
The category achieved double digit growth for the seventh consecutive year in 2018, growing by 20.4% year on year (yoy).
The fashion category also accounts for approximately half of buy now pay later transactions according to Australia Post. 
Source: Australia Post - Inside Australian Online Shopping 2019 eCommerce Industry Report
Although a relatively small segment of the overall fashion industry, activewear is the fastest growing category increasing by 37.5% in 2018. Women's fashion continued to perform strongly online, growing 22.6% nationally and accounting for 28.6% of all fashion purchases.
However in terms of growth, women's fashion has been overtaken by growth in the men's fashion and footwear categories growing by 24.9% and 23.8% respectively.
Source: Australia Post - Inside Australian Online Shopping 2019 eCommerce Industry Report
Geographically 73.9% of all online fashion purchases were made in metro areas, however fashion purchases in regional areas are growing faster than the national average, increasing by 22.3% yoy.
According to the report, almost 80% of eCommerce fashion purcahses were made in three states: New South Wales (36.4%), Victoria (26%) and Queensland (17.2%).
Source: Australia Post - Inside Australian Online Shopping 2019 eCommerce Industry Report
A trend that the report highlights - which will come as no surprise to many retailers - is that November is peak fashion month. 2018 marked the second consecutive year where November was the largest month for the category, peaking during Black Friday and Cyber Monday sales.
Australia Post GM for parcel and express services/intermediaries Ben Franzi said that the surge in online shopping was largely down to three factors.
"The surge in eCommerce was largely driven by the popularity of sales events, marketplaces and innovative buy now, pay later (BNPL) payment options.
"2018 was the year Australians fully embraced America’s Black Friday/Cyber Monday tradition, and is now the biggest week in our eCommerce history.
Source: Australia Post - Inside Australian Online Shopping 2019 eCommerce Industry Report
"These events have shifted what is usually our peak Christmas shopping period to November, with shoppers now expecting substantial discounts during this time.
"Marketplaces are dominating the eCommerce market, as consumers hunt for the best deals and the convenience of a one-stop-shop. The number of marketplace purchases grew by 31.2% year on year, indicating that more sellers are turning to marketplaces to broaden their customer base and grow brand awareness," he said.
According to Australia Post the online spend accounted for 10% of total retail spend in 2018 totalling $27.5 billion, an increase of 24.4% yoy.
To read the full report, click here.