It is a little bit of a grey area.
If you are a cash taxpayer, and you received (and paid) a bill in 2017, report the refund as income. Enter it as "Other Income".
If you pre-paid insurance in 2017, and deducted the expense on your 2017 return, you should amend the 2017 return.
https://ttlc.intuit.com/replies/6415925