Every pair of glasses you sell is two supplies. The split decides your VAT bill.

One sale, two supplies, and HMRC changed its mind about it

HMRC's original position was that dispensing formed part of a single taxable supply of spectacles. The High Court decisions in Leightons and Eye-Tech changed that, and HMRC's own guidance now accepts that dispensing — the measuring and fitting — is a separate supply from the goods. The sight test is always exempt. The frames, lenses, repairs and the accessories that go with them — cases, chains — are standard-rated.

That is not a technicality. It is the difference between handing over VAT on the whole ticket and handing it over on the goods alone, on every sale you make, every day you open.

Whether you can split at all is a three-stage test

HMRC works through it in order. First, whether the establishment is exempt in its own right: a body corporate registered under section 9 of the Opticians Act 1989, or a sole proprietor who carries out all the dispensing personally. Second, if not, whether the dispensing is done by — or directly supervised by — a registered optician.

If one of those applies, the total charge is divided between standard-rated and exempt. If neither applies, the supply is wholly standard-rated. Practices change: a registered optician leaves, supervision arrangements shift, a partnership incorporates. The VAT position moves with them, and it is rarely anybody's job to notice.

"Fair and reasonable, supported by valid calculations"

That is HMRC's standard for the apportionment itself. The method can be one of those in VAT Notice 700, or the Full Cost Apportionment method agreed between the optical bodies and HMRC. What it cannot be is a percentage somebody picked once and nobody has recalculated since — because the words that matter are supported by valid calculations, and on an inspection you are asked to produce them.

There is a simpler route that many practices overlook: no apportionment is needed at all where the charge for the goods and the charge for dispensing are separately disclosed. That is a decision about how you present a price to a patient, and it has a direct VAT consequence. It is worth taking deliberately rather than by default.

Exempt income means partial exemption, whether you have looked at it or not

Exempt supplies restrict input tax recovery. A practice with exempt dispensing income is partially exempt by definition, so the VAT on rent, equipment, professional fees and overheads cannot simply be reclaimed in full. The calculation has to be done, reviewed when the mix changes, and tested against the de minimis limits rather than assumed to be someone else's problem.

The test does not make the money. The dispensing does.

The economics of an optical practice run the opposite way round to how they look. The sight test occupies the clinical time and the appointment book, and it is the part of the business with the least margin in it. The money is made on what is dispensed afterwards — which means conversion rate, average dispense value and frame margin are the numbers that decide the year, and none of them appear anywhere in a set of statutory accounts.

Frames are fashion stock with a shelf life. A range bought two seasons ago and still on display is working capital standing still, and it is carried in your accounts at cost until somebody decides otherwise. Reviewed monthly it is a series of small, known decisions; reviewed annually it is a write-down nobody budgeted for.