A careful reader's walkthrough of the federal protections around outside caskets, the fees that cannot be charged, and the delivery questions worth asking first.

A funeral home cannot charge a fee for accepting a casket the family bought somewhere else. Any line item that appears only because the container came from outside is not permitted.
A casket bought from a retailer, a warehouse club, an online seller, or a woodworker two counties over arrives on a truck, at a loading dock or a side door, and someone has to be there to take it in. That logistical fact is where most of the trouble in outside purchases actually lives, not in the legal question, which was settled decades ago and is not close. The funeral home must accept it. What follows is what a careful reader checks between placing the order and standing in the arrangement room, in roughly the order those checks become urgent.
The Funeral Rule, enforced by the Federal Trade Commission, which oversees funeral goods and services disclosure nationally, bars a provider from refusing to handle a casket the family bought elsewhere and bars any charge for doing so. There is no handling fee, no receiving fee, no storage fee framed as a courtesy, and no adjustment to the basic services charge that appears only when an outside casket is involved. A provider also cannot require you to be present at delivery as a condition of accepting it. If a written price list or a verbal quote suggests otherwise, that is the moment to slow the conversation down and ask for the figure in writing.
Two documents carry the weight here: the general price list, which must be handed to you to keep at the start of any in-person discussion of arrangements, and the casket price list, which must be shown before caskets are displayed or described. Both exist so that the funeral home's own casket prices can be compared, line by line, against what an outside seller quotes. A third document, the itemized statement, arrives at the end and should show the casket line as zero or as a note that the container was supplied by the family. Read that line specifically. A statement that quietly reinserts a charge is the failure worth catching before you sign.
Online sellers commonly ship overnight or next-day for exactly this reason, but the shipment still has to land inside the funeral home's business hours, and a Saturday burial with a Friday afternoon delivery leaves very little margin. Call the funeral home directly, ask for the receiving address and the hours the dock is staffed, and confirm that someone will sign. Then give that address and those hours to the seller rather than assuming the two will sort it out. Ask the seller for a tracking number and the carrier's name, and ask what happens, concretely, if the truck is late or the box arrives damaged. A seller with a replacement policy will say so plainly.
A plain wood box from a local shop is often the better value and almost always the better-looking object, but it has to fit the grave liner or vault the cemetery requires, and vault interiors vary by manufacturer. Get the vault's interior dimensions from the cemetery in writing, give them to the builder, and confirm exterior length, width, and height including any handles or trim that stick out. Ask about the handles themselves: whether they are structural, whether they will carry the weight, and how many bearers the design assumes. Ask what the interior lining is, if any, and whether the lid is hinged or lift-off. These answers cost one phone call.
Ask the funeral home to inspect the shipment on arrival and to tell you the same day whether it is sound, correctly sized, and the model ordered. Damage discovered on the morning of the service is a different problem than damage discovered three days out, when a replacement can still be shipped or the builder can still make a repair. Keep the seller's receipt and the tracking record together with the itemized statement. That small folder answers nearly every question anyone raises later, including the ones from a probate attorney or an insurer.
The law is on the side of the family that shops around. Most of the remaining work is scheduling, measuring, and asking specific questions of specific people, early enough that the answers still leave room to act.