Well, there are a few different things that COULD happen.
If there is any question about whether the non-custodial parent received proper notice of the hearing, then the court might continue the matter to a later date.
If the suit and the notice have all properly been served on the non-custodial parent and the court has personal jurisdiction over that person, then the court might issue a Rule to Show Cause as the previous attorney mentioned.
If a summons to appear was issued to the non-custodial parent (usually comes with the pleadings in the J&DR court, but not in Circuit Court), then the judge may issue a capias (this is a bench warrant for the person's arrest, which essentially skips over the Show Cause phase all together).
As to your other question concerning failure to provide necessary information to determine child support, there are other ways to get this information and submit it to the court even if the other party fails to appear or respond in the case. This process is called Discovery and includes the ability to request the court to issue subpoena's to third parties for documents/information and to compel those third parties to appear as witnesses in court if necessary. Attorneys are also authorized by law to issue subpoenas as officers of the court -- so, if you have an attorney, your attorney can fire off the subpoenas.
These subpoenas (or subpoenas duces tecum if for documents/records) can be sent to the NCP's last and/or current employer, to financial institutions where they may have an account (which may be particularly helpful if the NCP is paid by direct deposit to a checking or savings account), a tax preparer, and/or any other third party that may be in possession of the NCP's financial and/or income information. If you show up in court with documented proof of the NCP's income and a proposed child support guideline worksheet and the NCP choses not to appear and argue or object, then the court can make findings and enter the child suport order and an Income Withholding Order to NCP's employer even in the NCP's absence.
If you are working through the Division of Child Support Enforcement, then they (DSCE) have access to IRS and state tax authority information (such as any W-2s, 1099s, etc. that may have been filed for the NCP by employers, banking institutions, etc.).
This response does not create an attorney-client relationship and is intended for general information purposes only.
Don't show up and expect a Show Cause (potential contempt).
Mr. Goldstein is a Virginia-licensed attorney only. The information is not, nor is it intended to be, legal advice. You should consult an attorney for individual advice regarding your own situation. Answering this question does not in any way constitute legal representation. Contacting Mitchell Goldstein or the Goldstein Law Group does not constitute legal representation, nor is any information you provide protected by attorney-client privilege until otherwise advised.
If he does not show up, or he does appear, but without his income information then you should seriously consider signing up with the Division of Child Support Enforcement. They have direct access to the Virginia Employment Commission (VEC) and as a result to all reported income within Virginia.