With springtime comes a new source of anxiety for employers: H-1B filing season. In a recent blog post, James Jensen of Porter Wright outlines what you need to know when it comes to the very coveted category of visas for foreign nationals working in “specialty occupations.”

Like daffodils, not every bulb you plant—or petition you file—will bloom: There are only 85,000 H-1B visas to be had each year, with 65,000 allotted to applicants with bachelor degrees and 20,000 for people with advanced degrees from American institutions. “We anticipate that the available H-1B visa numbers will again be exhausted within the first week employers are eligible to file,” Jensen says, which is on or after April 1. When that happens, a computer-generated lottery will select from the eligible candidates.