Small units, strict rules.

D4 Sparkling Wines and D5 Fortified Wines are the two smallest examined units of the Diploma and the easiest to underestimate. Each is a single sitting of 90 minutes that mixes theory and blind tasting, with its own pass rule. A candidate who knows the theory well can still fail on three wines.

This is an independent guide, based on the current specification and WSET's tasting guidance. Formats change, so check the WSET website before you plan. For the six units together, start with our guide to the Diploma.

What they cover

The two units are built the same way. Each asks you to understand what shapes the style, quality and price of the principal wines of its category: the growing environment, grape growing and winemaking, plus industry associations, labelling terms and wine business. Each also asks you to taste and evaluate those wines accurately.

• D4 Sparkling Wines. The principal sparkling wines of the world and the methods behind them, from the traditional method to tank and carbonation.
• D5 Fortified Wines. Sherry, Port, Madeira, Vins Doux Naturels and Rutherglen Muscat, with how each is made.

How each exam works

• One sitting. 90 minutes for an open-response theory paper and a blind tasting of three wines.
• Pass rule. At least 45% in the theory and at least 45% in the tasting, with an aggregate of at least 55%.
• The flight. The three wines may or may not share a theme, such as a country. If they do, the paper says so. In D5 the tasting may ask you to identify a wine's style within its category.
• Dates. Three set dates a year, in October, January and June.

The 45% rule

The rule stops one strong part from hiding a weak one. A brilliant theory paper cannot carry a tasting below 45% and a strong tasting cannot carry a theory paper below 45%. Above both floors, the aggregate must reach 55%.

The time is shared too. WSET's tasting guidance allows 45 minutes for a flight of three wines, no more than 15 minutes a wine, which leaves about 45 minutes for the theory if you keep to it. Decide your order before the day and hold to the clock.

Sparkling: method, then style

D4 answers turn on the link between how the bubbles were made and the wine in the glass. For each method, know the steps, the time involved, the cost and the style that results. Time on the lees after the second fermentation is the clearest example: it builds the autolytic notes of bread and brioche, at a cost in money and patience. Our article on reading a Champagne label covers the dosage and ageing terms that the theory paper expects you to use.

In the tasting, the mousse matters. WSET's guidance allows it to be part of the quality assessment for D4, so describe it and use it in your reasoning.

Fortified: when and how

D5 answers turn on two decisions: when the spirit is added and how the wine is aged. Spirit added during fermentation keeps natural sweetness, as in Port. Spirit added after fermentation gives a dry base, as in the dry styles of Sherry, whose style then depends on whether it ages under a layer of flor yeast or in contact with oxygen. Our guides to Sherry styles and Port styles set out those families.

In the tasting, fortified wines use their own alcohol scale. WSET's guidance sets low at 15 to 16.4% abv, medium at 16.5 to 18.4% and high at 18.5% and above. Sweetness must be judged with care: the guidance warns that calling a Rutherglen Muscat anything other than sweet can cost a palate mark.

Tasting three wines well

• Read the paper first. It introduces the flight and may contain information that helps you judge the wines correctly.
• One level per line. A range scores nothing. Choose one entry on each scale.
• Specific descriptors. Name the fruit, the nut or the spice, not the family.
• Reasons, not recipes. When you identify a style, explain which features in the glass point to it. Describing how the wine was made is a common mistake, as is repeating the tasting note instead of reasoning from it.

Reason from what is in the glass, not from how the wine was made.

When to sit them

After D1, the specification lets you take D3, D4, D5 and D6 in any order. With three dates a year, D4 and D5 can be fitted around the longer preparation for D3. Whatever the order, give each one its own tasting practice: a few flights of the category, against the clock, in the weeks before the exam.

Our Level 4 app, Worth Opening: WSET Level 4, rehearses D4 and D5 in their exam format: mock papers on the exam's clock, mark schemes point by point and home blind tastings of three wines, marked field by field against style notes for each category. Independent study aid. Not affiliated with, endorsed by or approved by the Wine & Spirit Education Trust.

Tasting is for adults of legal drinking age. Taste and spit, keep water and a spittoon to hand and never drive after a tasting.

Start with one flight

Have three wines of one category poured blind (perhaps three sparkling wines made by different methods) and give yourself 45 minutes. Write the full notes, then explain which method or style each one shows and why. If your reasons read like a production manual, rewrite them from what is in the glass.