Mortgage underwriters normally want documentation attached to the letter of explanation. For example, a letter of explanation may be required if a mortgage loan borrower had a substantial low income one year from the previous year and had a late payment history for three months.
Wage garnishment by itself will not damage your credit...and the fact that your wages are being garnishment will not be noted on your credit report....However, the judgment that led to the garnishment (if they report it) will affect your credit rating...and the original default of your credit card will also still damage your credit rating.
Limits on Wage Garnishment Amounts. Federal law limits the amount that can be garnished from your paycheck each week or month. The amounts vary depending on whether the creditor is a judgment creditor, student loan collector, taxing authority, or collector of child support. State laws also limit garnishment amounts.