What This Guide Covers
- The 24-month averaging rule and how it is calculated from your W-2s
- When declining overtime income must be excluded entirely
- Employer letter requirements and what the letter must say
- Shift differentials vs overtime: how the underwriting differs
How Underwriters Calculate Overtime Income
Overtime income is calculated by averaging the gross overtime earnings shown on two years of W-2s, divided by 24 months. If you earned $8,000 in overtime two years ago and $10,000 last year, the qualifying monthly overtime income is $750 ($18,000 divided by 24).
The critical rule is what happens when overtime income declines year over year. If your overtime earnings decreased from the prior year to the most recent year, the underwriter must use the lower figure rather than the two-year average. A borrower who earned $12,000 in overtime two years ago and $7,000 last year qualifies at $7,000 annually ($583 per month), not at the average of $9,500.
Overtime must also be likely to continue. The standard documentation is a YTD paystub showing overtime consistent with the prior two-year pattern, plus an employer letter confirming that overtime is available and expected to continue. Without the employer letter, many underwriters will not count the income even with a two-year history.
FHA follows the same framework as Fannie Mae for overtime. VA guidelines are slightly more flexible but still require documented history.
Required Documentation
- ✓Two years of W-2s showing overtime income (Box 1 must be verifiable against paystubs)
- ✓Most recent 30-day paystub with YTD earnings showing overtime consistent with prior years
- ✓Written Verification of Employment (VOE) or employer letter confirming overtime is available and expected to continue
- ✓If income is declining: explanation letter from employer documenting specific non-recurring reason
- ✓Two years of federal tax returns if other income sources are present
What Most Lenders Get Wrong
- 1.Averaging only 12 months of overtime instead of 24. Using a single year's W-2 overstates or understates qualifying income and is not compliant with agency guidelines.
- 2.Failing to require an employer letter confirming continuance. Without it, the income is technically unverified for continuation purposes and an underwriter can condition the file.
- 3.Counting overtime income when the YTD paystub shows a pace significantly below the prior year average without explanation. Underwriters who miss this will have the loan kicked back at QC.
- 4.Treating all extra pay as overtime. Shift differentials, hazard pay, and on-call pay each have different qualification rules and must not be lumped together.
Declining Overtime: When the Rules Work Against You
The declining income rule is the most common reason overtime income gets partially or fully excluded. If your overtime earnings dropped from year one to year two, even by a small amount, the underwriter must use the most recent year's figure rather than the two-year average.
The only way around this is documentation. If the decline was caused by a specific one-time event, such as a medical leave, a family situation, or a temporary reduction in available shifts during a slow period, a letter from the employer explaining the cause and confirming that overtime is again available can allow the underwriter to use the average rather than the lower year.
Without that explanation, the decline stands. A borrower who went from $15,000 in overtime two years ago to $9,000 last year qualifies at $9,000, period. If $15,000 is what they need to hit their target price, they need to either wait a year for their earnings to recover and be reflected on the next W-2, or reduce their target price.
The practical implication for Kern County borrowers, where oil field, agricultural, and manufacturing overtime is common and highly seasonal, is that filing timing matters. Applying for a mortgage during the high-overtime season, when YTD figures are strong and trending above prior year, is a meaningfully better position than applying when YTD is lagging.
Overtime vs Shift Differentials: A Critical Distinction
Overtime and shift differentials are often lumped together on paystubs but are treated differently in underwriting.
Overtime is pay for hours worked beyond the standard 40-hour workweek at a premium rate (typically 1.5x). It is variable by nature and follows the two-year history and continuance rules described above.
Shift differentials are additional pay for working non-standard hours: nights, weekends, or holidays. They are often a fixed percentage above the base hourly rate rather than an overtime premium. For many employees, particularly nurses, law enforcement officers, and manufacturing workers, shift differentials are essentially guaranteed as long as the employee works those shifts, making them more predictable than overtime.
Fannie Mae allows shift differentials to be treated as base income if the differential is part of the borrower's regular compensation structure and is documented as consistent and ongoing. This is a more favorable treatment than overtime, because it does not require the same two-year averaging analysis under the variable income framework.
For nurses at Kern Medical or correctional officers at one of the Kern County facilities, this distinction often makes a meaningful difference in qualifying income. Getting the characterization right upfront prevents underwriting conditions later.
Overtime income qualification is a math problem, but the math only works if you pull the right numbers from the right documents. I see lenders who use the paystub YTD figure, divide by the number of months elapsed, and call it qualifying overtime income. That is not the agency method. The agency method uses W-2s averaged over 24 months with a specific declining-income test applied. Getting that wrong costs borrowers real dollars in qualifying income.
Do you have overtime income and want to know how much of it qualifies?
Call Dan at (661) 342-9381. He will review your specific situation and documentation in a free call.