I just looked at the 2018 instructions for Form 8885 at
https://www.irs.gov/pub/irs-pdf/i8885.pdf. Here is a cut and paste from it on Page 5 under the heading "Required Documents":
All health plans. For all health plans, you must include all of the following documents.
1. An official letter reflecting that you were an eligible individual for the months claimed on line 2 in 2018.
• For trade certified individuals demonstrating TAA, ATAA, or RTAA eligibility—A copy of the official letter from the Department of Labor, your state workforce agency, or employment office stating you are eligible for trade adjustment benefits.
• For PBGC eligibility—A copy of the official letter or a copy of your 2018 Form 1099-R, Distributions From Pensions, Annuities, Retirement or Profit-Sharing Plans, IRAs, Insurance Contracts, etc., from the PBGC showing you received a benefit paid by the PBGC.
2. A copy of your health insurance bills or COBRA payment coupons for each month you are claiming the credit on
line 2.* The bills must have:
a. Your name (or name of the policy holder),
b. The name of your health plan,
c. Your monthly premium amount,
d. Dates of coverage, and
e. Your health plan identification number(s).
*If your health plan doesn’t provide members with an insurance bill or COBRA payment coupon, you must provide health plan enrollment documents or an official letter from your health plan that has the required information listed under items 2a through 2e above. If your monthly premium includes amounts that don’t count towards the HCTC, such as dental or vision coverage or coverage for family members who aren’t eligible for the HCTC, your documentation also must specify those ineligible amounts.
3. Proof of payment for each month you are claiming the credit on line 2 such as:**
a. Canceled checks (copy of front and back),
b. Bank statements,
c. Credit card statements, or
d. Money orders.
**Your proof of payment must indicate the amount paid and to whom it was paid. If you don’t have one of these types of proof of payment, contact your health plan for a record of your payment(s).
So yes, the 1099-R is one piece of proof.
Tom Vicker