Ch7. Numbers, Dates, and Units in US Professional Documents

Number-Writing Principles

Based on the US Government Publishing Office (GPO) Style Manual and Chicago Manual of Style.

Basic principles:
- Quantities and amounts: use Arabic numerals
- Statute and regulation references: Arabic numerals
- Numbers in narrative prose: spell out one through nine; use figures for 10+

Rules:
① Quantities and measurements: Arabic numerals
   Preferred: 3 people, 50 items, December 31
   Avoid: three people, fifty items (in data-heavy official text)

② Thousands separator:
   Use commas: 10,000 / 1,250,000
   Narrative shorthand: "$1 million" or "10,000 units"

③ Mixed millions/thousands:
   $125,300,000 → "$125.3 million" (narrative)
   → Use word-form unit markers for readability

Dollar Amount Formatting

Amount notation:
① Formal/contract: "$3,500,000" or "three million five hundred thousand dollars"
   → Contracts, budgets, and official financial documents

② Narrative: "$3.5 million"
   → Reports, memos, descriptive text

③ Written-out parallel (high-stakes contracts):
   "Four million five hundred thousand dollars ($4,500,000)"
   → Anti-fraud / anti-tampering notation

Notes:
- Never drop the dollar sign in amounts: "3.5 million" (✗) → "$3.5 million" (✓)
- Foreign currency: "€3,500" or "3,500 euros (approximately $3,800 USD)"

Date Formatting

US professional document date principles (GPO Style Manual):
- Month Day, Year — spelled-out month or numeric MM/DD/YYYY
- No trailing period on standard dates

Correct forms:
May 13, 2026         ← standard narrative
05/13/2026           ← numeric form (forms, tables)
2026-05-13           ← ISO 8601 (technical/international documents)

Common errors:
- 5/13/26 (✗ — ambiguous two-digit year)
- 13/5/2026 (✗ — day-first is non-US convention)
- May 13th, 2026 (✗ — ordinal suffix unnecessary in formal prose)

Date ranges:
May 1–December 31, 2026   ← en-dash, no space
FY 2026 (October 1, 2025 – September 30, 2026)

Fiscal year:
FY 2026 (not "Year 2026 budget" → "FY 2026 budget")

Time Formatting

12-hour format (standard US):
2:00 PM, 9:30 AM, 6:00 PM

24-hour format used in:
- Military / law enforcement documents: 14:00, 09:30, 18:00
- International / technical documents

Avoid ambiguity:
"After 10:00 PM" (✓)   vs.   "after 22 hours" (non-US usage)

Units of Measure

Area:
- Square feet (sq ft) or square meters (m²) — specify system used
- Acres for land: "100 acres"
- Avoid informal units in formal documents: "10,000 sq ft" (✓)

Distance / Weight:
- US customary: miles, feet, pounds, tons (short ton = 2,000 lb)
- SI when required by contract or regulation: km, kg, metric ton
- "100 miles" (✓), "100 mi." (abbreviated in tables)

Currency:
- USD: $3,500 or "USD 3,500" (international contexts)
- Foreign: "€3,500 (approx. $3,800 USD)"

Percentages:
- Use % symbol: "10%" (✓) / "10 percent" (✓ in formal narrative)
- Don't start a sentence with a numeral:
  → "The rate exceeded 10%." (✓)
  → "10% exceeds the threshold." (✗) → "The 10% rate exceeds the threshold." (✓)

Abbreviations and Symbols

Foreign terms and technical jargon:
- Define acronyms on first use: "Artificial Intelligence (AI)"
- GDP, CBO, OMB — spell out on first use in non-specialist documents

Numbers with legal references:
- Section 1, Paragraph 2 → "§ 1" or "Sec. 1" in tables; spell out in prose
- "Section one" (✗ in formal usage) → "Section 1" (✓)

Ellipsis:
- "…" (three dots) for omissions in quoted text
- Use sparingly in formal documents

US Professional Date Format ★★★★★ : May 13, 2026 — spelled-out month, comma before year. ISO 8601 (2026-05-13) for technical/international use. Memory tip: Month DD, YYYY — spell the month, comma before year.

Dollar Amount in Millions ★★★★★ : $125,300,000 → "$ 125.3 million” in narrative. Always include the $sign. *Memory tip: Always attach the unit — never "$ 125.3” without “million” in prose.*

Area Units ★★★★☆ : 1 acre ≈ 43,560 sq ft ≈ 4,047 m². Use acres for land, sq ft for buildings in US documents. Memory tip: Formal US area = sq ft / acres; m² when SI required.

Practice Quiz

Q. How do you write “May 13, 2026” in a formal US government document?

May 13, 2026 (spelled-out month, comma before year). Numeric form 05/13/2026 is acceptable in tables and forms. ISO 2026-05-13 for international/technical contexts.

Q. How do you write “$3,500,000” in a US contract narrative vs. a report?

Contract: “Three million five hundred thousand dollars ( $3,500,000)" for anti-fraud clarity. Report narrative: "$ 3.5 million” or “$3,500,000.”