Representative Jeff Miller, a Florida Republican who is chairman of the House Veterans Affairs Committee, said whistle-blowers at several veterans hospitals had told his staff members that they would be threatened if they failed to alter data to make patient-access numbers look good for their supervisors, one reason he has called for a criminal investigation into the Veterans Affairs hospital system.

“Fear was instilled in lower-level employees by their superiors, and those superiors did not want long wait times,” Mr. Miller said in an interview. “Bonuses are tied directly to the waiting times of the veterans, and anybody that showed long wait times was less likely to receive a favorable review.”

The precise role incentives and performance reviews might have played in falsifying waiting-list data remains unclear. In Phoenix, the inspector general’s office said, investigators plan to interview scheduling supervisors and administrators to “identify management’s involvement in manipulating wait times.”

But documents suggest that using the data in annual performance reviews may be commonplace. One review at a Pennsylvania veterans medical center showed that a significant portion of the director’s job rating was tied to “timely and appropriate access,” which would include waiting times for doctor appointments. One of those goals would be met only if nearly all patients were seen within 14 days of their desired appointment date — a requirement not found in the private hospital industry.

Schemes to disguise wait times generally followed a handful of approaches, whistle-blowers and officials in Congress say. In Phoenix, where administrators were overwhelmed by new patients, many veterans were not logged into the official electronic waiting list, making it easier to cloak delays in providing care.

Another strategy, according to documents and interviews, was for Veterans Affairs employees to record the first date a doctor was available as the desired date requested by the veteran, even if they wanted an earlier date.