Firms are allowed to print their logos or advertising on their invoices along with compulsory information, said Vu Thi Mai, deputy director of the General Department of Taxation.

Earlier this year the Government required firms to print their own invoices instead of having to acquire invoice forms from tax agencies, as was the case before January 1. These so-called red invoices serve as official proof of commercial transactions for taxes and other purposes.

However, many businesses have complained they still face difficulties in printing invoices, especially businesses who generate a large amount of invoices.

Some say authorities should provide businesses with a sample invoice, as there was still confusion over all the information that needs to be included on a legal invoice.

Mai said the department will continue to guide firms on how to ensure they comply with the new decree.

Businesses do not need to send documents and sample invoices to tax agencies before printing the invoices, said Mai.

"Invoices for water, electricity and telecommunications services without user signatures are also valid," she said.

Small firms that have less than 10 employees are allowed to continue to buy invoices from tax agencies until the end of 2011./.