Does the PR have authority to counter my offer without going back to the heirs first

The letters testamentary are the key document, but they only tell half the story.

In most independent administration probates, the PR has full authority to contract for sale without heir ratification on each individual decision, that authority flows from the court's grant, not from ongoing heir consensus. The heirs' signature on a purchase agreement is a separate question from whether the PR can negotiate price, and in many states those are not the same event. The PR negotiates, the court confirms (or in independent administration, may not require confirmation at all), and the heirs' recourse is to object at confirmation, not to unwind a signed contract.

Take a property under contract at 400k. The PR signed, two heirs are cooperative, one is unreachable. At a confirmation hearing, the court can accept the contract, require overbidding, or flag the missing heir, but the buyer who contracted in good faith with a PR acting within their letters generally has a protected position. The risk is not usually "deal falls apart because the heir objects to the price." The risk is delay, a confirmation hearing that opens overbidding, or a judge who wants proof of service on the absent heir before proceeding.

What you actually need to know is whether this probate is operating under independent administration authority or supervised administration, because that changes everything about confirmation requirements. Your attorney can pull that from the court file in about ten minutes, and it is worth the cost of that call before you close the gap.

What state's probate code governs this estate?

This is a real question and the answer genuinely depends on Arizona law and the specific grant of authority in those letters testamentary, so the definitive read has to come from a probate attorney licensed in Arizona. One conversation with the right person costs far less than a deal that unwinds at confirmation.

That said, here is how this generally works so you can ask better questions.

A personal representative, sometimes called an executor in other states, gets their authority from two places: the letters testamentary the court issues, and Arizona's probate statutes. In many independent administration situations, the PR can negotiate and accept offers without going back to the heirs for approval on each step. The heirs are beneficiaries of the estate, not co-sellers on the contract. The PR signs the purchase agreement on behalf of the estate, and the heirs receive their share of the net proceeds after the estate closes. So a counter coming back without visible heir consultation is often completely normal.

The complication you are sensing is real though. Arizona probate sales sometimes require court confirmation, meaning a judge approves the sale price before it closes. If this estate is subject to confirmation, any heir or interested party can show up at the hearing and object. That is the moment the unreachable heir becomes a practical risk, not the counter itself.

The two things I would verify with a probate attorney before you close the gap are: whether this estate is operating under independent or supervised administration, and whether the specific sale requires court confirmation. Both answers change your risk picture significantly.

What did the listing agreement or the estate's attorney say about whether court confirmation is required on this one?

The PR's authority to negotiate and counter typically flows from the letters and from whether Arizona required this estate to go through full supervised probate or independent administration, and that distinction matters more than the face of the letters themselves. Under independent administration, a PR can often bind the estate to a contract without prior court approval or heir ratification of each negotiating step, but the sale still usually requires a notice period during which any heir can object before closing. Full supervised probate in Arizona runs differently and may require court confirmation of the sale price, which is where a dissatisfied heir gets a formal forum to argue the number was too low.

The checklist a careful buyer runs here: confirm whether the estate is under independent or supervised administration by pulling the order admitting the will or the order appointing the PR, not just the letters; ask the PR's attorney in writing whether a Notice of Proposed Action has been or will be issued covering this sale; identify whether the unreachable heir received proper notice of the probate proceeding at all, because a heir who was never properly served has standing to reopen issues that a properly noticed heir waived; and get a title commitment ordered now so the title company flags any recorded interest the missing heir might hold.

The practical protection at closing is a probate sale endorsement on your title policy, and your title company should require the PR to produce evidence that the statutory notice period ran and no objection was filed before they will insure. The question I'd press is whether the PR's attorney has actually confirmed in writing that independent administration is in effect here, because that single fact changes almost everything about your exposure.