Alimony in solido (also referred to as lump sum alimony) is alimony in the nature of a final property settlement award that is not subject to change. It is an award of a definite sum of money to be paid in a lump sum or as installments over a definite period of time to make up for an imbalance in property division. It does not terminate upon the death of either party.
Per Topic No. 452 Alimony and Separate Maintenance on the IRS website:
Amounts paid to a spouse or a former spouse under a divorce or separation instrument (including a divorce decree, a separate maintenance decree, or a written separation agreement) may be alimony or separate maintenance payments for federal tax purposes. Certain alimony or separate maintenance payments are deductible by the payer spouse, and the recipient spouse must include it in income (taxable alimony or separate maintenance).
A payment is alimony or separate maintenance only if all the following requirements are met:
For more information regarding Alimony, please refer to IRS Publication 504 Divorced or Separated Individuals and go to page 12.
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.