I have a porcelain veneer and the tooth has a cavity. Do I have to get a new veneer after the cavity is filled?

Veneers that are covering the tooth can not cavity, but your tooth that is supporting the veneer can get cavity.
In most cases the veneer can be saved by removal of the cavity and bonding the filling to the existing tooth. Depending on where the cavity is, the dentist and you will make a decision if it can be blended or you need to redo your veneer. Usually if the cavity is from the palatal side, or lingual side and the xtent of cavity is not large, you can salvage the veneer.

Thanks for asking the question. Well, that totally depends upon the tooth cavity. If the cavity is minor and veneers is not affected with it then your dentist will clean the tooth and use the older veneer otherwise you need new one after tooth filling.

Often, the decay can be removed and the cavity filled with a white filling material that blends with the veneer. No guarantee, but often we can do this. Hopefully, your cavity is small enough for it to go this way. 

Hi, thanks for sending your question. Depending on the size of the cavities the veneers may or may not be disturbed. Its important not to wait for the treatment since that can only complicate the outcome.All the best.

The answer depends on where the cavity is related to the veneer and how deep the cavity is. The veneer can be weakened by the decay being in the tooth. 

Hi:Depending on how accessible, large and deep s the cavity you may or may not have to redo your veneer.Best,Dr. Maddahi

When you get a cavity next to or just on the same tooth as a veneer, it can be repaired with composite tooth colored filling material BUT it can be likely that the tooth supporting the veneer is becoming weaker or the seal of the veneer to the tooth is breaking down.....so many things can be happening hence, you may benefit from a full coverage "ceramic crown" more so than just a veneer.  Both should look highly cosmetic but the crown can strengthen the tooth where as a veneer is basically a false facing on a tooth.