If your husband was working as a sub-contractor, the person that paid him should have issued to your husband Form 1099-NEC reporting the income that this person paid to your husband.
This is the way it should have been done if your husband is Self-Employed and the person that paid him is also a business person that "hired" him to do a job.
When someone does work for an Employer, that Employer withholds income taxes and submits that withholding to the IRS and state (if state tax is withheld). The Employer also withholds FICA Tax, which is Social Security and Medicare. FICA tax is paid half from the Employee pay and half that the Employer pays.
When someone does work as a sub-contractor, that person has a business and does work for other contractors or customers. They follow their own rules since they do not have an Employer. They pay their own taxes, including both halves of the FICA Tax.
If this person that paid your husband did not issue paychecks with paystubs, and did not issue a W-2, they were treating your husband as if your husband has his own business.
YOU HAVE TWO OPTIONS:
1. Your husband can file as a Self-Employed taxpayer. Your joint return will include Schedule C to report the income your husband made throughout the year doing this type of work.
The good news is that your husband would be able to deduct business expenses, such as a vehicle, tools and work supplies.
The bad news is that your husband would need to pay all his own taxes.
This is all done though the tax return you file together.
In TurboTax enter the income under
Wages & Income
Business Income and Expenses (Schedule C)
It will require an upgrade to TurboTax Self-Employed Online or TurboTax Home and Business Desktop
2. Your husband can file a complaint with the Department of Labor and also use Form 8919 to report that the other person should pay half the FICA Tax because they (your husband) claims that they were an employee, not a subcontractor.
If he was told how to do the work, what time to show up, etc. he might be considered an employee by law.
In TurboTax enter the income under
Wages & Income
Less Common Income
Miscellaneous Income, 1099-A, 1099-C START
Other income not already reported on a Form W-2 or Form 1099 START