The empowered committee on value added tax (VAT) today said lack of uniformity in VAT rates among states was a serious issue, and advanced its meeting to April 15-16 to consider the matter."We are ready to admit that VAT rates are not uniform (among states). That is why we have advanced our meeting, which was earlier scheduled for May, to April 15-16," Ramesh Chandra, empowered committee secretary, said today.On traders' grievances over VAT, he said doors of negotiations were open, and asked the traders to present their case before the committee.On the controversial issue of VAT on CSD canteens, he said it was up to the defence and finance ministries to give concessions to these canteens.