The receiving company. You will get a 1099R from invesco for the withdrawal/rollover to enter into your tax return. You get the 5498 showing the amount deposited in the new account. You really don't need the 5498. You don't enter it into your tax return.
The 5498 is from the receiving end verifies that they received the funds as a rollover. That form is usually issued in May so if the rollover was after May then you probably will not receive it until the next May.
It is important to receive and keep the 5498 as proof of the rollover in case the IRS ever questions it.
You'll only get a Form 5498 if the receiving account in an IRA. I couldn't find anything on the Milliman website that indicates that Milliman provides IRAs or IRA-based employer plans.
Oh. This was just a 401k roll over. So what document do I provide to the IRS to "prove" the funds were rolled over?
None, unless the IRS requests it, then the account statement from the receiving account should be sufficient to show the deposit.
If the 1099-R for the distribution has a code G, then that is a direct rollover so it should not be questioned but sometimes the IRS wants conformation. If they do then they will ask for it.
It seems that the IRS has been becoming more skeptical lately about whether claimed rollovers to qualified plans are actually completed, even more so if the rollover was done indirectly rather by a code-G direct rollover. You might consider including an explanation statement with your mailed tax return to substantiate that the rollover was actually completed, otherwise just be ready with account statements from the receiving plan that show the receipt of the rollover in case the IRS questions the rollover.