Vatting whisky without losing the thread: records HMRC (and your blender) will thank you for

A vatting looks simple from the floor: empty casks into a vat, mix, move on. On paper it is the single most record-intensive moment in a whisky's life. Alcohol changes identity — from N individual casks to one batch — and every litre has to be accounted for across that boundary. This guide covers what to record, when, and the mistakes that make stock refuse to balance. General guidance, not tax advice.

What a vatting is, in record-keeping terms

Whether you call it vatting, marrying, batching or blending, the structure is the same:

• Inputs: a list of casks, each with its measured volume and strength at disgorge — not its fill figure. Regauge first; a ten-year-old book figure can be 10%+ out.
• Operation: the spirit is combined, possibly reduced with water, possibly filtered, possibly returned to casks or sent to a bottling tank.
• Outputs: what the operation produced — a tank at a measured volume and strength, refilled casks, or cases if it feeds straight into bottling.
• Losses: inputs minus outputs, in litres of pure alcohol. Pipework retention, filtration, spillage, samples.

On the W1, the outputs appear as increases resulting from operations and the losses as losses resulting from operations— while each input cask's book-vs-actual gap lands separately as a loss in storage. Three lines, one operation.

The two losses hiding in every vatting

This is the distinction that trips up most spreadsheets. When you disgorge a cask:

1. Storage loss:book figure (what your ledger said the cask held) minus measured figure (what you actually poured out). That alcohol left over years of maturation — the angel's share — and it only becomes visible now.
2. Operational loss: the sum of all measured inputs minus the measured output of the vatting. That alcohol left today, in your pipes and filters.

HMRC asks for them on different lines because they mean different things: one is warehouse performance, the other is process performance. Merge them and a leaking cask can hide behind a sloppy transfer — or an efficient operation can be blamed for losses that happened years before.

A worked example

A vatting of three casks into a bottling tank:

The tank, after mixing and a light filtration, measures 561.5 LPA.

• Losses in storage: 71.3 LPA (attributed per cask)
• Losses in operations: 563.8 − 561.5 = 2.3 LPA (~0.4% — a healthy transfer)
• Increase from operations: 561.5 LPA of new batch stock
• Age of the batch: 2016/0077 is the youngest input, so the batch can carry at most a 9-year age statement in 2026 — however old the other casks are.

Every number on that list ends up somewhere: the W1, the batch record, the label, the costing.

The month-end cut-off

A vatting physically done on the 30th but signed off on the 2nd belongs to oneperiod, and it must be the same answer every time. Pick a rule — commonly, the date the spirit actually moved — and apply it to the input casks, the output and the losses together. The classic error is the inputs leaving the cask ledger in September while the output appears in October: for one month-end, 560-odd LPA simply doesn't exist, the W1 won't balance, and someone spends a day finding alcohol that was never missing.

Where vatting records go wrong

1. Vatting from book figures. Yields disappoint, duty planning is wrong, and the storage loss gets silently buried inside the operational loss.
2. No per-cask input list.The batch exists but can't be traced to casks — fatal for age statements, single-cask claims, recalls and audits.
3. Splitting the operation across periods (inputs in one month, outputs in the next).
4. Forgetting water. Reduction adds volume but no alcohol. Track bulk litres and LPA separately or the strength maths stops working.
5. Unrecorded samples. The lab and tasting draws from the vat are losses.
6. Returned remnants. Spirit put back into a cask after the vatting is a new fill event, not a footnote.
7. Overwriting the batch when it is adjusted. A top-up or correction should be a new recorded event; editing the original breaks the audit trail.
8. Age by average. The batch's age is its youngest component. One mis-keyed cask year and the label on ten thousand bottles is wrong.

How Provenate records vattings

Provenate is distillery management software built around exactly this operation:

• Cask-level inputs, measured not assumed. Each input cask is disgorged at its regauged figure, and its storage loss is calculated and posted automatically.
• Two losses, two lines. Storage loss (book vs measured) and operational loss (measured in vs measured out) are separated the way the W1 asks — no manual splitting.
• Outputs become stock. Tanks, refilled casks or bottling runs created by the vatting enter the ledger as increases from operations, in the right period, under a single cut-off rule.
• Full thread preserved. From any bottle, back through the bottling run and the vatting, to the individual casks and their fills — the trace HMRC, the SWA and your blender all want.
• Age computed from the youngest cask, so the statement on the label is defended by the record, not by memory.

Want to see a vatting recorded start to finish? Book a demo.

Official sources

• Excise Warehousing: Excise Warehouse Return (W1) form and notes
• Receive goods into and remove goods from an excise warehouse (Excise Notice 197)
• The Scotch Whisky Regulations 2009