It keeps official data in place.
Starting from a pre-filled declaration reduces the risk of retyping values that AT already has.
Guide
What is a pre-filled IRS declaration?
Portal das Financas can create a declaration with data AT already knows, such as Portuguese salary, withholding, pensions, and many deductible expenses.
Rent is usually part of Portal data.
When rent was correctly communicated to AT, it should appear in deductible-expense data instead of being typed from scratch.
Missing annexes still need attention.
Foreign income, foreign accounts, special regimes, or manual corrections may still require extra annex work.
Related: rent and e-Fatura deductions.