I want to sell t-shirts to multiple niche markets, for instance liberals and conservatives (political affiliations). I want each brand to be isolated, only selling liberal shirts on the liberal branded site and conservative shirts on the conservative site. I have a few more niches in mind, like martial arts, but they are all t shirts.

I have an LLC and thought to get a DBA (doing business as) for the LLC matching the brand of each site. I want folks who buy shirts from the conservative site to see the conservative branded dba on their credit card statement and folks who buy shirts from the liberal site to see the liberal branded dba on their credit card statement. Same idea for martial arts, they see the martial arts dba on their credit card statement.

How many merchant accounts do i need? Can I use only 1?

I think in this case you will have to open a separate merchant account for each t-shirt you sell. :) just kidding.

Do not try to re-invent a wheel. Select a neutral DBA for your business like SHIRTSONLINE ili E-SHIRT whatever, and sell everything through one merchant account.

You'll need an EIN for each business, and then you can have a separate merchant account for each brand. However, I agree with the poster above... it might make more sense to have some sort of generic named parent company.

You can only have one descriptor per merchant account. Its possible to have a single EIN with different merchant accounts for each DBA. Most processors will allow any descriptor you want within reason, and within the character limit (usually around 25). The processor's main concern will be that the descriptor is something that is recognizable to the cardholder and that it contains a phone number (ideally toll-free) so that the cardholder can contact you if they have questions about the charge. If the URLs/DBAs are very different from each other, and could confuse cardholders, then most processors would prefer you to have a seperate merchant account for each DBA.

If the customer doesn't recognize your business, they will initiate "do not recognize charge" disputes and annoy the card banks and cause you a lot of extra work.

I think that the most efficient way for you to go about this would be to have a primary label and secondary label and web site for each political/affiliation.

As an example, say your parent company name was "SUPER T" T-Shirts.

You may want to setup a single merchant account called SUPER T T-SHIRTS and then have a Web site for something like:

SUPER-T-REPUBLICAN.COM
SUPER-T-DEMOCRAT.COM
SUPER-T-MARTIALARTS.COM
... etc ...

The above are just examples but basically - the customer would be able to recognize the 'primary' marketing label to avoid chargebacks and then you could just slightly customize the domain for the other affiliations to isolate them from one another.

This would also allow you to process everything under a single merchant account since it is all trully and legitimately one business. I don't even think you would necessarily need multiple DBA's with the above structure.

I have been told by Cybersource that First Data-South Platform accepts dynamic soft descriptors. That means you can pass a unique descriptor with each transaction. I have seen this done with Video Professor.

There charge appears as:

VIDPROF 1STS&H
VIDPROF 2NDS&H
VIDPROF EXCEL

I know Vital does not allow it and First Data-Nashville & Tampa do not. There are a lot of processors and platforms outthere and your gateway or software will need to be configured.

Check out mainstreetsoftwareThey have software that replaces gateways and also list processors they are certified with.