2026-08-30

Six-minute increments and the rounding rule your clients expect

Legal billing runs on tenths of an hour. Consulting often runs on quarters. Both need a written rounding rule, and both need a tool that does not quietly apply its own.

The convention

A six-minute increment is 0.1 of an hour. Most firms that use it round partial increments up: a 20-minute call is 0.333 hours and bills as 0.4. Others round to the nearest tenth. Quarter-hour firms do the same at 0.25. Bill4Time and CosmoLex lay out the variations. The rule that matters is the one in your engagement letter.

Write it down, apply it once

Rounding belongs at invoicing, in one place, applied the same way every month. It does not belong in the time entry. If the entry is rounded at the moment it is typed, the record no longer says what happened, and two people logging the same call produce different numbers.

What Winnows stores

Whole minutes, exactly as entered. A 20-minute call is 20 minutes in every report. The billing export carries exact hours and the amount at the entry’s rate, and your invoicing tool applies the rounding rule your client agreed to.

One consequence worth knowing if you import from Harvest, which stores hours to two decimals: 0.33 hours is 19.8 minutes and becomes 20. The reconciliation report counts every entry that rounded, says how many minutes moved in total, and keeps Harvest’s own amount for those entries so money still matches to the cent. In a 32,000-entry account it was 18 entries and 0.4 minutes.

What to check in any tool

• Does it store what you typed, or what it rounded?
• Can the rounding rule differ by client?
• Is the rule applied at invoicing, where it can be changed, or at entry, where it cannot?