I usually switch cars several times a year, but usually sell my car to
a individual or dealer and buy my new car at a different place,
therefore paying sales tax on each car.  The reason I switch cars
often is because I put a lot of miles on them, so when I sell it I
lose money, but get a car with less mileage.  Any how, I was told you
can only save on the taxes if you trade in your car where you buy it,
which I don't know for certain.  Is there a way for me to save on
sales tax when I buy a different car?

Hello.

Yes, it's true that the way you can reduce sales tax on a vehicle in
Texas is by trading in one or more vehicles at the same place where
you buy your new vehicle.

From Texas' "Window on State Government": Motor Vehicle Taxes
"Will a trade-in reduce the taxable value?
    The value of a motor vehicle received by the seller as
consideration on the purchase of another motor vehicle reduces the
taxable value of the purchase."
http://www.window.state.tx.us/taxinfo/mtr_veh/faqmoveh.html

As explained on the web page of the Bell County Tax
Assessor-Collector:
"Taxable value equals Purchase Price less any Trade In
Sales Tax is 6 1/4% (Six and one quarter percent) of the Taxable
value"
http://www.bellcountytx.com/taxassessor/btxvehratestax.htm

Let me illustrate how you would save sales tax by trading in your old
vehicle at the same place you buy a new vehicle.

Let's say that the car you want to buy is $20,000.  Let's say that
your old car is worth $5,000.  If you sell your old car somewhere
else, then you pay 6.25% of the full $20,000, or $1,250 in sales tax.
But if you trade in your old car at the same place that you buy your
new one, then you pay 6.25% of $15,000 ($20,000 minus the $5,000
trade-in), or $937.50 in sales tax, a savings of more than $300.

On the other hand, you have to consider whether the trade-in value
that the dealer gives you is the same as the price you could sell the
car for somewhere else. If the dealer is offering to let you trade in
your old vehicle for $5,000, but you could easily sell it to some
other person for $6,000 then you'd be better off doing the latter
because the extra $1,000 would exceed the $300 sales tax savings.

If you do decide to trade in your old car where you buy your new one,
be aware of these rules listed on Texas' "Window on State Government":

"Only a motor vehicle can be traded in on the purchase of another
vehicle to reduce the taxable value. Tax is due from the purchaser on
the trade difference. Other items can be accepted as trade-ins, but,
however, they cannot be used to reduce the taxable value."

"A trade-in vehicle is not required to be titled in the name of the
person trading it to the seller as long as the vehicle is actually
traded to the seller."

"More than one vehicle can be traded in on the purchase of a motor
vehicle."

"A vehicle of greater value than the vehicle being sold may be taken
in trade. This is referred to as a 'trade down,' and no tax is due. No
credit is allowed."

"A motor vehicle can be traded to a seller prior to delivery of the
vehicle being purchased. This might occur when a vehicle has been
ordered, and the trade-in is delivered to the seller prior to delivery
of the new vehicle to guarantee the trade allowance."

For more information, visit Texas' "Window on State Government": Motor
Vehicle Tax Manual
http://www.window.state.tx.us/taxinfo/audit/mv/4a.htm

search strategy: texas vehicle, sales tax, trade-in, taxable value

I hope the helps.