What goes on the register, and what does not
The test is whether you would want to find the purchase date in a hurry. That covers anything with a warranty worth claiming, anything with a serial number, and anything an insurer would ask about after a fire or a break-in. It does not cover consumables, hand tools, or the sort of thing that is easier to replace than to look up. A register that lists two hundred items is a register nobody maintains.
Six columns carry almost all of the value: what it is, when it was bought, how long the warranty runs, the serial number, what it cost, and where it lives. The last two are the ones people leave out and later want, because the price is what an insurance conversation runs on and the location is what turns the register into an inventory you can actually walk around with.
Adding months to a date is not obvious
An item bought on August 31 with a six month warranty expires on a date that does not exist, because February has no 31st. Two conventions are in use. Clamping moves it to the last valid day, so the answer is February 28, or February 29 in a leap year. Overflow rolls the surplus into the following month, giving March 3. Both are defensible and they differ by up to three days.
This page clamps, and says so on the output. Three days rarely matters, but it matters exactly when it matters, which is a claim filed at the very end of a cover period. If that is your situation, the date that governs is the one in the warranty document, and the register is a prompt to go and read it rather than a substitute for having done so.
There is a second wrinkle worth knowing: the date a warranty runs from is not always the purchase date. Delivery date, installation date and registration date all appear in warranty documents, and for something installed weeks after it was bought the difference is real. Enter whichever date the document uses and note it in the item name if the two differ.
The lapsing window is the working part
Everything else on the page is a record. The window is a prompt. Set it to a period long enough that you could actually get a service call scheduled inside it — sixty to ninety days suits most equipment — and look at that list rather than at the whole register.
What you are looking for on that list is the machine with a fault you have been tolerating. Intermittent problems get lived with until they become permanent ones, and the point at which they become permanent is frequently just after the cover ended. A fault raised while the warranty is live is a service call. The same fault raised two months later is an invoice.
Serial numbers, and photographing the plate
The serial number is the field most often left blank and most often needed. Manufacturers ask for it before they will discuss anything, insurers ask for it after a theft, and recall notices are issued against ranges of them. The number is stamped on a plate that will outlive any drawer you file the receipt in, so the reliable habit is to photograph the plate and the receipt together the day the thing arrives and to keep those photographs somewhere that is not the machine.
Extended service contracts sold at the till are a different product from a manufacturer warranty and they have their own terms, their own start date and their own exclusions. If you have one, list it as a separate line with its own expiry rather than adding its months to the original, because they do not always run consecutively.
Related paperwork
For a household version weighted toward replacement value rather than warranty dates, the home inventory value tool is the closer fit, and the warranty basics guide covers what these documents typically do and do not promise. When something on this list finally fails, the repair or replace calculator weighs the repair against a new one, and the appliance replacement budget calculator spreads the expected replacements across future years so the next one is not a surprise.
Questions people ask
How do I write the warranty length?
As a plain number of months, or with a suffix: 36, 36m and 3y all mean the same thing. A blank column leaves the item as unknown unless you set a default in the field below the list, which is deliberate — an assumed warranty length is worse than an admitted gap, because it produces a confident expiry date with nothing behind it.
Why is my expiry date a day or two off what the manufacturer says?
Most likely the month-end rule, or the start date. This page clamps a month overflow to the last valid day while some systems roll it forward, which can differ by up to three days. And warranties do not always run from the purchase date — delivery, installation and registration dates all appear in real documents. Enter the date the document actually uses.
Does a warranty transfer if I sell the item?
Sometimes, and it depends entirely on the manufacturer's terms and on the kind of product. Some transfer freely, some transfer once with a fee and a form, and some end at the first sale. There is no general rule to report, and consumer protections that sit alongside a manufacturer warranty vary by state. Read the document, and if the answer matters to a sale, get it in writing before the money moves.
Should I register products with the manufacturer?
Registration requirements vary by product and by manufacturer, and so does what registration actually buys you. What is worth knowing is that registration is often how a manufacturer reaches you with a safety recall, which is a reason to do it that has nothing to do with warranty claims. Keep the proof of purchase regardless, because that is what almost every claim asks for first.
Can I use this for insurance purposes?
It gives you the list an insurer will ask for — item, date, price, serial, location — which is most of the work. What it is not is evidence. Photographs of the items and the receipts are the evidence, and they need to live somewhere that survives whatever event makes you need them, which means not solely in the building the items are in.