When Can the Tax be Refunded?
Sellers located in counties that border the United Mexican States (Mexico) may not issue a refund until 24 hours after the time of export listed on the documentation. These counties are El Paso, Hudspeth, Jeff Davis, Presidio, Brewster, Terrell, Val Verde, Kinney, Maverick, Dimmit, Webb, Zapata, Starr, Hidalgo and Cameron. For example, if a customer buys a stereo from a store in El Paso and takes it across the border into Mexico (exports it) at 2:00 p.m. on Tuesday, the purchaser cannot return to the seller and receive a refund until after 2:00 p.m. on Wednesday.
Sellers located in all other counties in Texas may not issue a refund until the seventh day after the date of export shown on the documentation.
Note that any use of the property in Texas by the owner prior to export causes the loss of export exemption. For example, if a customer buys a hat in Texas and wears it, the purchaser may not request a refund of the tax paid on the hat even if the purchaser subsequently exports it when leaving the United States. Wearing the hat is a taxable use of the item in this state.
[ Taken from http://www.window.state.tx.us/taxinfo/taxpnw/tpn2010/tpn1012.html#issue8 ]
