What is Form 8958?
IRS Form 8958 (Allocation of Tax Amounts Between Certain Individuals in Community Property States) is used by couples who reside in the community property states of Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, or Wisconsin and are filing separately.
Its purpose is to report the income and tax allocations (how the amounts are split up, divided, apportioned, assigned, etc.) for each member of the couple.
For guidance in handling community property income and taxes with TurboTax, see Married Filing Separately in Community Property States.