Tax Form Req'd for Aquatic Therapy

I have been studying this forum, but have not run across info re the tax form suppliers must fill out in order to deduct (or not charge) sales tax.

I'm in DFW area in Texas.
I finally got design completed, Oncor, City, and TESS (Tx excavation safety system) approval and permits for a 21 x 41 Doughboy, countersunk.

My Dr actually suggested swimming therapy for knee and back injury. That's what got me interested in a pool to begin with. I have Rx and a letter from Dr.

Four suppliers can order the pool; lead time 3-8 business days. One actually has 1 in stock; however, of the four in my area who sell it, the one with it in stock, for some reason, is not able to confirm if they are allowed to not charge taxes. Does anyone know specifically how to get a copy of the reuired tax form for 'aquatic therapy'? I am not trying to get out of paying what is due; however, if I can reduce my total cost by $600, I'd like to save that and get started asap. I have installers waiting to start work.

My second question is chlorine or what? I've read and read this forum and still cannot decide which system to go with. All suppliers have opinions re max countersink depth and type of chemicals.

I have heard from all four suppliers, "in order to maintain warranty, you can only use... or countersink ....". When I ask for that in writing, it cannot be provided.

I apologize in advance if this is in the incorrect forum.

Regards,
Teri Schmig

I have no idea what you are asking, except that you want a tax form. And I have no idea what "countersinking" has to do with chlorine.

For the tax form, call the Texas Dept. of Revenue, Sales Tax Division. http://www.window.state.tx.us/taxinfo/sales/

Sorry.

Thank you for replying!

Yep - searched IRS.gov and http://www.window.state.tx.us/taxinfo/sales/ site and called IRS Before posting the question...
Seller finally called competitors for correct mystery info. Seller was misinterpreting requirements, per their legal and accounting advisers, and requesting multiple docs. Better safe than sorry, for their sake.
Countersink and chlorine are not related. Just got same statement, "in order to maintain warranty" reply from 4 diff retailers with 8 diff answers to two separate questions, 1st - regarding countersunk depth, and 2nd - regarding chemical system.

I have yet to find the actual Dough Boy document stating what countersink depth and what chem syst, if any, will void the warranty. Maybe another mystery or I haven't asked the right people yet.

Thanks again for your time!