Patients who think they're getting an annual checkup often end up with an unexpected bill. The Good Brigade/DigitalVision Collection via Getty ImagesI was teaching health economics when a student raised his hand. We were discussing the Affordable Care Act, or ACA, which requires most health plans to cover certain recommended preventive services at no additional cost to patients. I explained that preventive care could cost nothing.The student had expected that, too. Instead, he said, he received a bill for more than US$500 after his checkup. He was so frustrated that he said he would never go back for another annual checkup. I suggested he contact his insurer to find out why he had been charged and whether his visit had been billed as preventive care. Then another student spoke up. Her husband had paid several hundred dollars for what he thought would be a free checkup too.The very next day, I received a $78 bill for my own Pap smear. I expected my insurance to cover this cervical cancer screening without cost-sharing because it is among the preventive services recommended by the U.S. Preventive Services Task Force and generally covered under the ACA.When I called my insurer, I learned that the visit had been billed as a regular outpatient office visit, with no mention of the Pap smear. I then called my primary care provider’s office. The clinic acknowledged a coding error and corrected it. My bill dropped to zero.As an assistant professor of health policy and addiction studies at Penn State Harrisburg, I know whom to call and what questions to ask when I receive an unexpected medical bill. Many of my graduate students worked full time and took evening classes. Would they know how to dispute a bill, or have time?Those experiences led me to investigate how often patients pay out of pocket for annual checkups. I teamed up with fellow researchers Erin Duffy and Max Crowley to examine this question. In our analysis of a Pennsylvania survey, nearly 1 in 4 insured respondents reported paying for their most recent checkup.Why a preventive visit may come with a billMany health care services covered by insurance are subject to copayments or deductibles. A copayment is a fixed amount patients pay for a covered service, while a deductible is the amount they generally must pay for covered care before insurance starts paying.The ACA, however, requires most health plans to cover certain recommended preventive services, including screenings for high blood pressure and certain cancers, vaccinations and counseling to help people quit smoking. These should come at no cost to patients.Generally, this applies when patients see providers who are in their insurance plan’s network. But that doesn’t mean every annual checkup is free.If a patient discusses a new symptom or asks the clinician to manage an existing condition during their annual checkup, it can result in a separate office-visit charge. A test may be billed as diagnostic rather than preventive, and coverage varies by plan and provider. Sometimes, as in my case, a coding error is responsible.Not every charge is inappropriate. The challenge is that patients often cannot tell which services should be covered, why they were billed, or whether a mistake occurred.What our survey foundPrevious studies have found, using insurance claims, that patients sometimes face out-of-pocket costs during preventive visits. But these records show how visits were billed, not necessarily what patients believed they were receiving. We wanted to know whether people who thought they were getting annual checkups also reported paying out of pocket.Our study, published in August 2026 in the peer-reviewed journal Prevention Science, used the 2024 Penn State Lion Poll, an online survey of Pennsylvania adults. We analyzed responses from 912 insured adults who reported an annual checkup within the preceding 10 years. Most had one in the past year.Of those respondents, 23.5% reported paying out of pocket for their most recent checkup. Among those who paid, the average reported out-of-pocket amount was $68.50. After accounting for other characteristics such as age, gender, insurance type, income and education, we found that respondents who were not familiar with ACA preventive-care protections were about 12 percentage points more likely to report paying than those who were familiar with the protections. That difference is equivalent to roughly 12 more people paying out of every 100. Those who considered healthcare unaffordable were about 13 percentage points more likely to pay than those who found it affordable.Because our survey relied on patients’ reports rather than billing records, we could not determine why individual charges occurred, or whether they were appropriate. The findings show associations, not causation, and our nonrandom sample cannot provide a precise statewide estimate. How doctor visits are billed doesn’t always match what service patients think they are receiving. adamkaz/E+ Collection via Getty Images Why these bills matterI kept thinking about the student who said he would never return for another checkup. Research has shown that even modest out-of-pocket costs can discourage people from getting recommended screenings. Delaying preventive care could mean missing opportunities to detect health problems early, when treatment may be more effective.Our survey did not find a statistically significant association between paying for a previous checkup and planning another one. However, respondents who were unfamiliar with ACA protections or considered healthcare unaffordable were less likely to plan a checkup. These findings suggest that uncertainty about costs may discourage people from seeking preventive care.What patients can doBefore a visit, ask your insurer which preventive services are covered without cost-sharing and confirm that your provider is in-network. Ask the clinic whether discussing other health concerns or receiving additional tests could trigger a charge.If a bill arrives, compare it with your insurer’s explanation of benefits, which you can typically find in your online insurance account or receive by mail. Ask the provider’s billing office which services and codes were submitted and request a correction if something appears wrong. You can also contact your insurer to question or appeal a coverage decision.A colleague told me she challenged a $20 or $30 copayment requested at check-in for an annual visit after remembering our conversations. The charge was removed.Patients should not have to become experts in insurance billing to receive preventive care. Clearer coverage information and more transparent billing could help people seek care without fearing unexpected costs.Read more of our stories about Philadelphia and Pennsylvania, or sign up for our Philadelphia newsletter on Substack.This project was supported, in part, by funding from Penn State’s Social Science Research Institute (SSRI). The content is solely the responsibility of the authors and does not necessarily represent the views of SSRI or Penn State.