Find the model and serial number when something breaks.

The model number identifies the product line, so it's what you need for spare parts, manuals and repair bookings. The serial number identifies your exact unit, and manufacturers usually ask for it to check warranty cover or recalls.

Both are normally printed on a rating plate, also called a data plate, data badge or type plate: a sticker or metal plate that also lists the electrical or gas ratings. Brands label the numbers differently, so look for words such as Model, Mod., Type or Product code, and Serial, S/N or Ser. No.

Open the door and look along its top and side edges, then around the frame of the tub. Bosch puts a label or engraving on the top or side rim of the door. Samsung lists the top of the door. Whirlpool lists the left side of the tub frame on built-in models.

A torch, or your phone's camera held at an angle, helps when the label is on an edge you can't see straight on.

On a front-loader, open the door and look around the opening. Bosch usually puts the label on the inner rim of the door, and sometimes behind the filter flap or on the back. Samsung says to check around the door near the seal, then the back.

On a top-loader, look under the lid and on the back of the machine. Whirlpool lists the tub rim, under the lid.

Most front-loading dryers follow the same pattern as washing machines. Bosch puts the label on the inner rim of the door, behind the filter flap or on the back. Samsung lists the area around the door, then the back. Whirlpool lists the rim of the door opening, or behind the water tank on ventless models.

If your dryer sits on top of a washer, read the label on the back with your phone camera rather than unstacking the machines.

Start inside the fresh-food compartment: the side walls, the ceiling and the area behind the bottom drawers. Bosch says its label is visible when you pull out the bottom salad or freezer drawer. Samsung puts its label inside on the left-hand side, with a second label outside at the bottom left. Whirlpool lists the left-hand wall inside the fridge compartment, or the right-hand wall on side-by-side models.

If the inside label is behind a shelf you can't remove, a photo taken with your phone held inside is often enough to read it.

For ovens and ranges, open the door and look around the frame of the oven opening, then the storage drawer if there is one. Bosch puts the label on the outer rim of the oven, visible when the door is open. LG lists the left side of the door frame or the drawer. Miele puts it behind the control panel on ovens where the panel lifts up.

On a built-in hob, the plate is usually underneath, which you can't see once it's fitted. Don't lift a hob out of the worktop yourself. Check the manual and the original box first. Miele also supplies a second data plate in the accessories pack, and some Miele induction hobs can show the model and serial number on their display.

Open the door and check the frame around the opening and the inside walls. Whirlpool lists the front frame, visible with the door open, on over-the-range models, and underneath the control panel on built-in models.

A built-in or over-the-range microwave can't be turned round, so the frame behind the door is the place to look before anything else.

On a wall-hung boiler, look on the underside and the top, and on the front panel. Ideal Heating says its label is usually at the bottom left, and that you may need to open a panel to see it. Only a qualified engineer should remove the casing itself.

Furnace locations vary by maker and age, and the rating plate is often behind an access panel. Check the owner's manual for where it is on your model, and switch off the power before opening a panel. If the panel needs tools, ask your technician to note the numbers at the next service.

The installer's paperwork is often the easiest route. The commissioning certificate the installer filled in (the Benchmark checklist in the UK) usually records the boiler's details, and a recent service report may list both numbers too. Ideal also says the original manual names the model on its cover or first pages.

Tank and tankless water heaters carry a rating label on the outside of the casing. Rheem says the serial number on its rating labels has ten digits and starts with the month and year of manufacture.

The serial number often encodes the manufacture date, which helps when you're working out the heater's age or warranty. The format differs between makers and years, so use the manufacturer's own lookup or support line to decode it rather than a generic chart.

A split system has a label on the indoor unit and another on the outdoor unit, and each can have its own model number. Photograph both. Daikin says to check the right-hand side or bottom edge of a wall-mounted indoor unit, and a side or back panel of the outdoor unit.

Portable and window units usually carry the label on the side or back of the casing. LG says its window, wall and portable units have the label on the right side as you face the unit.

Empty the water tank and drip tray, then look underneath. De'Longhi says the model number, a mix of letters and numbers such as ESAM4200.S, is usually on a rating plate at the base.

Nespresso says its serial number is printed on a sticker on the drip tray or under or on the back of the machine, and on the original box. It is 19 characters long and starts with 0 or 1.

Labels fade, peel off or end up behind a fitted panel. The numbers are often recorded somewhere else, so check these before you contact the manufacturer.

If none of them has the number, contact the manufacturer's support team with the brand, roughly when you bought it and clear photos of the appliance and any label remains. Have the retailer's name ready, because the retailer may be able to find your order.

Once you've found the numbers, keep them where you'll look next time: the purchase date, warranty, receipt location and past repairs belong in the same place.

A photo of the plate in a named album works. So does a single page kept with the manual.

To make that page, fill in the free appliance passport.