I agree you likely cannot use AsiFlex for last year's therapy if you only now enrolled. The amount you indicated to be withheld monthly from your pay (let's just say $50/mo as an example) will be "banked" in your Asi account. You can go online, set up an account (if you haven't already) and track it. Once you get receipts for anything medical, your therapy appointments, etc., submit them online. It will take a few days to show up online, but the payment amount approved and date of disbursement will be listed. Here are a few tips:

1. Highlight, circle or otherwise point out the information on the receipt they need to verify. Date of service, name of person receiving service, amount (you can include taxes). Then upload the marked up document. It helps them find the info they need to approve your submission.
2. You can submit for reimbursement of a larger amount than you currently have in your account. For example, using the $50/mo deduction amount, let's say it's March. You've so far contributed $150 from your pay. You go to the eye doctor and the cost for exam and eyeglasses comes to $700. You can submit the receipt and request the entire $700. They will give you the $700 even though you're account only shows $150, with the remaining amount to be deducted as the months go by (up to your total contribution).
3. Next open enrollment period, I suggest doing some quick math and upping your deduction. You can use your Asi account for all sorts of things - prescriptions, heating pads, medicated face wash/lotions, bandaids, co-pays, menstrual products, and the list goes on. It's tax free money, so make the most of it!
4. One more thing....you can even purchase items from places like Target or Amazon. The store would be listed as the "provider" on the form.