One of the risks many individuals fear in retirement is a market loss as they approach or enter retirement. The NewRetirement Planner does not currently account for negative returns in the Accounts section. However, the Planner does have a Monte Carlo simulation driving your Chance of Success which accounts for negative returns because it models variability and negative returns are very possible.
If you would like more manual control, one option would be to model a "disbursement' from an account at a specific date. This may have tax consequences so you may want to select "deductible" for the disbursement.
Example: If you have a $1,000,000 401k and you want to view the impact of a 30% market loss you may want follow these steps:
STEP 1: Create a new Scenario
STEP 2: Navigate to My Plan > Expenses and Healthcare > Disbursements
STEP 3: Press Add a Disbursement
STEP 4: Enter a Disbursement for the desired account
STEP 5: When asked "Is this disbursement tax deductible?" select Deductible
STEP 6: Add detailed notes
STEP 7: Press Save
Step 5: Navigate to Scenario Management and use the Scenario Comparison feature to compare the scenario under your Pessimistic, Average and Optimistic Assumptions as well as with your Baseline and other scenarios.
