If you're itching to jet off abroad this year, you'll need an up-to-date passport. The recent uptick in passport renewal requests (and the accompanying backlog due to heightened demand) may have already prompted you to get a head start on your application. But to sidestep an unanticipated setback, there are some important factors to consider before submitting your paperwork. [See: 10 Frequent Flier Secrets Every Traveler Should Know.]"It always pays to do things in advance," says Andres Rodriguez, community relations officer for the U.S. Department of State in the Office of Passport Services. He recommends giving yourself plenty of time prior to your trip to dodge a dreaded delay. "When someone submits a passport application and there's an issue, they'll receive a notification from us," he explains. Once the information request letter is sent, applicants have 90 days to submit the requested information, or they must restart the application or renewal process, he says. And while routine processing times take six to eight weeks, it's best to renew three months ahead of your trip, he adds. Aside from slow processing times, many countries have stringent entry and exit policies requiring passports to be valid for six months after your trip. That's yet another reason to start the passport-renewal process early. "Once your passport has about one year of validity on it, you should probably at least start to think about [renewing it]," Rodriguez says. With that in mind, U.S. News identified six unexpected reasons you may hit a passport-renewal stumbling block.Submitting a Noncompliant Photo A passport-compliant photo must meet rigorous standards for size, background and facial expression. According to Rodriguez, submitting an inadequate photo is the "number one reason someone could experience a delay with their passport processing." Lighting is a primary issue, he explains. Aside from the photo needing to render the subject's face on a plain white background, any sign of a shadow or even a camera setting that could inadvertently alter an image to make a face look digitally imposed is problematic, he explains. In this case, there's a good chance the application will get kicked back to the applicant, he says. Other common passport photo snags include cropping the image in a way that alters the outline of the subject, Rodriguez explains. And as of November 2016, passport photos with glasses will no longer be accepted. A full list of image requirements is available on the State Department's website.Given that the essential requirements for an approved passport photo is extensive, "the hassle of taking your own photo and making sure it meets exacting requirements is more trouble than it's worth," cautions Jeff Klee, CEO of CheapAir.com. Instead, he advises getting your photo taken for a small fee at a drugstore chain. Walgreens, for instance, offers government-compliant ID photos for $13.99. Providing Insufficient Proof of Citizenship"With national security being much tighter than it's been, you have to make sure you have the valid requirements," cautions Tom Spagnola, senior vice president, supplier relations at CheapOair. Higher scrutiny, coupled with a greater volume of passports being issued, makes it essential for applicants to submit the proper documents, which include proof of citizenship, a passport photo, a completed application (a DS-11 for applications or DS-82 for a renewal) and proof of identity, such as an expired passport, a valid driver's license, a certificate of citizenship, a U.S. military ID or a valid foreign passport, he adds.Invalid evidence of citizenship could derail your application, Rodriguez explains. And keep in mind photocopies of a birth certificate, rather than an original copy, are not accepted. Another caveat: If you were born outside of the country, additional materials (think: a certificate of naturalization) are required.[Read: What You Need to Know About Upcoming Passport Changes.]Parental Consent IssuesConsent issues for minors under 16 are a common cause of delayed applications, Rodriguez explains. Not only must two parents show their relationship as parent or legal guardian, they must also appear in person to issue consent. "It can get complicated quickly for divorced parents, those under custody agreements and/or for persons owing back child support," Klee says. "If your family circumstances fall into one of these categories, you should allow extra time to get appropriate advisement, processing and to complete the required paperwork," he cautions. While every situation is different, it's best to be prepared before heading to your closest acceptance facility, Rodriguez adds.Supplying Insufficient Payment or Failing to Pay Child Support Providing the correct payment for the type of passport book (and card) you want is essential for expediting your application, Klee cautions. "You can pay fees directly at a passport acceptance agency, by mail, at a third-party agency or from abroad in an emergency," he explains. Checks and money orders are accepted for applications submitted by mail or at an acceptance facility; credit cards, exact cash, checks and money orders are accepted forms of payment at passport agencies. For an adult passport renewal, the cost, which includes a processing fee, is $140. Beyond submitting the correct paperwork and fee, if you owe child support of $2,500 or more, you may not be eligible for a passport. If an applicant owes this amount of child support, there will be a block in the State Department's system and the applicant would have to go to the U.S. Department of Health and Human Services to get it removed, Rodriguez explains. Also, keep in mind that it can take two to three weeks for your name to be removed from the block after HHS is alerted that you've settled your payment. Applicants have 90 days to address the issue and comply, Rodriguez adds. Inconsistent Information or a Missing SignatureIf there's a disparity in your signature on a standard DS-11 or DS-82, your application may be declined. For example, if you forgot to sign a DS-82 by mail, you may need to go to an acceptance facility for the request to be properly executed, Rodriguez cautions. In short: Before you submit, make sure you've signed all required documentation correctly and sufficiently. [Read: 5 Things You Need to Know About the New U.S. Passport Design.]Unpaid Tax Debt A new rule mandates that applicants with delinquent tax debt will be denied a passport. According to a State Department official, the Fixing America's Surface Transportation Act, put in place in 2015, bans the department from issuing a passport to those persons certified by the IRS as having a seriously delinquent tax debt and allows the department to revoke passports previously issued to these individuals. According to an official, updates pertaining to the new procedures in compliance with the FAST Act will be posted in the future on travel.state.gov.