Beware using the USPS ScanForm.
First, my post office (and likely yours) does not scan the individual items on the form before sending them out. This means that the parcel numbers are not trackable and neither is the ScanForm number. The customer sees only that you have created a label and you cannot see the progress of your item either.
Recently one parcel was lost and though it is on the ScanForm and I got a receipt at the counter, the USPS says that my receipt does not prove acceptance by the post office for insurance claims. This is hard to understand because it does not make sense. In other words, though the receipt says "acceptance" on it, the parcel was not accepted in the sense of assuming liability.
Luckily, the underwriter for Stamps.com insurance (same for Endicia, I think) does honor the ScanForm, though one has to wait 30 days and get an affidavit or letter from the customer stating that the item was never delivered. The underwriter (PIP 800-325-7390) told me that they do not pay out just on the basis of the USPS trail going cold of a parcel that is not delivered for 30 days, but will instead believe the customer saying it was not delivered.
I spent half a day on the phone with the underwriter, Stamps.com, and the USPS trying to sort this out. I got different stories from different employees and my post office told me an entirely different story from those. I could find nothing in writing and no one could direct me to any written policy about this. In a quaint aside, my postmaster said that she could write what is called a "local letter" stating that she personally saw the parcel come over the counter and that the post office would consider that in an insurance claim.
Post office workers on our route don't always scan the ScanForm or the parcels, so I have to drive into town and take parcels to the counter of the post office to make sure they have been officially accepted. I thought that the ScanForm covered me and saved me time, but it turned out to be a nightmare. I lost two parcels in a few weeks, combined value of $1400. My postmaster told me yesterday that "in my case" one should NEVER use the USPS ScanForm again. I was tempted to find out in what case one would want to use it, but didn't go there.
My first thought is to make the customer happy and replace the parcels, then work out the insurance settlement separately. I cannot trust the post office anymore and will likely switch to UPS.
Recouping the money is important, but the stress and time of tracking down answers and solutions is something to factor in.
I know a lot of people will lecture me on what the official policies and procedures are but my experience showed me that the only thing that matters is the individual employees you deal with and the information/misinformation they are acting on. It can be a many layered problem, though it shouldn't be.
I have self-insured for years and never lost a parcel until this recent double loss. I still self-insure for inexpensive items that are easy to replace but for all else, I insure to the gills. Private insurance from PIP appeals to me because it covers the case of misdelivery with delivery confirmation. In a case like that, with the customer claiming the parcel was not delivered and the post office claiming it was, I want an insurance company to sort it out.
Do your own research and be prepared.