In case a foreign Company seconds its employees to Vietnam to survey market, if these employees meet the conditions on residents in Vietnam according to the regulations at Article 1 of Circular No. 111/2013/TT-BTC , incomes from salary, wage and other benefits earned in Vietnam shall be subject to 20% PIT (Article 18 of Circular No. 111/2013/TT-BTC ).
In case the company in Vietnam agrees to pay on behalf of its parent company outside Vietnam expenses in relation to the employees seconded to Vietnam to survey market, if these expenses do not belong to incomes liable to PIT according to Article 3 of Law No. 04/2007/QH12 (amended at Law No. 26/2012/QH13 and Law No. 71/2014/QH13), it is not required to withhold and pay tax in Vietnam.