If a person posts bail for someone and the person does not show for trial is the one who posted bail responsible for the rest of the money?

Yes.

It’s important to remember that the bail premium is never refundable in any condition, as the premium is earned by the bail company for service rendered upon the release of the defendant. Even if the case is dismissed or the charges are dropped, the bail premium paid to the agency is always non-refundable.

When signing a bail bond contract, you (the indemnitor) will take on the following responsibilities:

The first and foremost responsibility is that you (the indemnitor), along with the help of the bail agency, will make sure the defendant returns to every one of their court dates without fail.

Should the defendant fail to return to court, you will also take on the responsibility of paying additional fees, if the bail company has to hire a fugitive recovery agent to bring the defendant back to court.

Finally, if the defendant cannot be located, you (the indemnitor) will be made solely responsible to pay for the entire amount of the bail originally set by the court. If collateral was taken (such as real estate lien or pink slip) at the time of signing the contract, that will be used to pay towards the bond and will not be returned.

When someone does fail to go back to court, a judge will issue what is called a “bench warrant” for the arrest of the defendant. The bail that was originally paid will be forfeited and a recovery agent will be contacted to locate the person who ‘skipped bail.’

Bail companies realize that cars break down, children get ill, and some may miss a court date because of extenuating circumstances. However, most indemnitors’ and defendants don’t realize that these issues can be easily taken care of by the bail company with just a simple phone call to them as soon as the defendant misses a court date.

https://www.scvbailbonds.com/bail-faqs/when-i-sign...

What If They Don’t Show Up For Their Court Dates?

Let’s say you have some valid concerns about whether or not the person you are considering bailing out will fail to appear at their court date. You probably want to know your risks. In the event of a skipped court appearance, the bail bond is said to be in default. Now you are at risk of losing all the money you put up to get your friend or family member out of jail. You are also at risk of losing the collateral you used to secure the bond, which could be your house, car or other possessions. There are a few options to remedy the issue, though they vary from state to state.

In most states, the court will send a notice to the bail bond agency letting them know the accused has failed to appear at court and that the bond is now in default. There is generally a grace period to make things right, but it is given at the discretion of the court, which may not be so lenient depending on the history of the accused. A bench warrant will then be issued for their arrest.

Bailed Out of JailOften, there will be a statutory period of time--usually around 90 days--where you will be able to turn the accused in to get your bond out of default status. This usually simply involves bringing the person who skipped their court date to the police and filling out some paperwork that will notify the court the person has been returned. Alternatively, if the person happens to be arrested pursuant to the bench warrant, then you can go through the same process to request your bond to be taken out of default.

If the state you reside in allows it you have the option of hiring a fugitive recovery agent, more commonly known as a bounty hunter, to track down the defendant and return them to custody. This will have the same practical effect as if they were arrested pursuant to the bench warrant and you will have to fill out the applicable paper work to take your bond out of default.

Unfortunately, if all of the above fails, the cash or collateral you put up for your friend will be forfeited to the court and you will not see one penny returned, no matter the circumstances.

https://www.aboutbail.com/pages/what-if-the-person...

Yes you are

When you post bail you either come up with all of it or pay ~10% down to a bail bondsman. If the person doesn't show for court then the bondsman pays and comes after you for the rest. This is why they generally require you to put up something of value like your house.

YOU are the one that is guaranteeing that the person will show up. So it's only fitting that YOU be the one to pay. Who else would pay? The person on the run?

Yes you are

Yes and that is why you do not post bail for other people