The company had originally intended to complete the £11m sale of the division before the end of October, but it said the deal will now be signed on 17 October and the transaction will complete by 15 November.
In a statement to the London Stock Exchange, UBC said because of recent changes in the commercial radio industry in the UK, both parties have agreed to a further two weeks of due diligence.
UBC Media could earn future payments totalling £5.5m in cash depending on the performance on the division in the 12 months following he sale.
Once the commercial division has been sold, UBC will consist only of its production and interactive divisions.
United Kingdom
UBC announces completion date for sale of commercial arm
LONDON - UBC Media has announced it will complete the sale of its commercial division to US-based radio company Global Traffic Networks next month.