Portfolio Rebalance Tax Calculator

Purpose

Rebalancing is necessary to maintain your target allocation, but selling winners in a taxable account triggers capital gains taxes. This skill finds the path from current allocation to target allocation that minimizes the tax bill — often saving thousands of dollars through smart sequencing, account selection, and lot optimization.

The naive approach (sell everything overweight, buy everything underweight) can be extremely costly. A tax-aware approach might achieve the same result at a fraction of the tax cost.

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Information Gathering

Required

1. Current portfolio: All positions across all accounts with:
   • Ticker, shares, current value
   • Cost basis and purchase date (for taxable accounts)
   • Account type (Taxable, Traditional IRA, Roth IRA, 401k)
2. Target allocation: What they want to move to (e.g., 60/40 stocks/bonds, specific fund targets)

Needed for Tax Calculation

3. Filing status and estimated taxable income
4. State of residence
5. Realized gains/losses this year already

Helpful

6. Expected new contributions (401k, IRA) — can use these to rebalance without selling
7. Timeline: Urgent (do it now) vs. gradual (over months/year)
8. Cash available to deploy
9. Capital loss carryforward

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Rebalancing Strategies (Ranked by Tax Efficiency)

Strategy 1: Contribution-Based Rebalancing (Zero Tax Cost)

Direct new money to underweight asset classes:
- 401(k) contributions → buy underweight funds
- IRA contributions → buy underweight funds
- New cash savings → buy underweight funds in taxable

Tax Cost: $0
Timeline: Slow (depends on contribution amounts)
Best For: Small imbalances, patient investors

Strategy 2: Tax-Advantaged Account Rebalancing (Zero Tax Cost)

Sell/buy within IRA or 401(k) only — no tax consequences:
- Sell overweight positions in IRA/401(k)
- Buy underweight positions in IRA/401(k)

Tax Cost: $0
Timeline: Immediate
Limitation: Only rebalances the tax-advantaged portion; taxable account unchanged

Strategy 3: Dividend/Distribution Redirect (Zero Tax Cost)

Redirect dividends and capital gains distributions:
- Turn off reinvestment (DRIP) on overweight positions
- Use the cash to buy underweight positions

Tax Cost: $0 (dividends are taxed regardless)
Timeline: Gradual
Best For: High-yield portfolios

Strategy 4: Tax Loss Harvesting Rebalance (Negative Tax Cost!)

Sell positions that have losses AND are overweight:
- Realize the loss (tax benefit)
- Buy target allocation with proceeds
- Net result: rebalanced AND reduced taxes

Tax Cost: Negative (you save money)
Best For: After market downturns

Strategy 5: Selective Lot Selling (Minimized Tax Cost)

When you must sell in taxable:
- Sell highest-cost-basis lots first (smallest gain)
- Sell long-term lots before short-term lots
- Sell loss lots first (tax benefit)
- Avoid lots approaching long-term status (wait if possible)

Tax Cost: Minimized through lot selection

Strategy 6: Asset Location Shift (Gradual, Tax-Efficient)

Over time, restructure which assets are in which accounts:
- Taxable: Hold tax-efficient assets (US index ETFs, munis)
- Tax-Advantaged: Hold tax-inefficient assets (bonds, REITs, intl)
- Gradually make swaps when opportunities arise

Tax Cost: Depends on execution
Timeline: 1-3 years

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Calculation Workflow

Copy this checklist into your working response and tick items off as you go:

Rebalance Tax Plan Progress:
- [ ] Step 1: Map current vs target allocation
- [ ] Step 2: Identify zero-tax rebalancing moves (IRA / 401k / contributions / DRIP)
- [ ] Step 3: Optimize taxable-account sales (lot selection)
- [ ] Step 4: Calculate total rebalancing tax cost (compare options A / B / C)
- [ ] Step 5: Generate phased action plan
- [ ] Disclaimers included

Step 1: Map Current vs. Target

                    Current     Target      Difference
US Stocks:          $XXX (XX%)  $XXX (XX%)  +/-$X,XXX (over/underweight)
Intl Stocks:        $XXX (XX%)  $XXX (XX%)  +/-$X,XXX
US Bonds:           $XXX (XX%)  $XXX (XX%)  +/-$X,XXX
Intl Bonds:         $XXX (XX%)  $XXX (XX%)  +/-$X,XXX
REITs:              $XXX (XX%)  $XXX (XX%)  +/-$X,XXX
Cash:               $XXX (XX%)  $XXX (XX%)  +/-$X,XXX

Step 2: Identify Zero-Tax Rebalancing Opportunities

Before selling anything in taxable, exhaust these options:

Available Zero-Tax Moves:
1. Rebalance within IRA:           Can shift $X,XXX
2. Rebalance within 401(k):        Can shift $X,XXX
3. Redirect next contributions:    $X,XXX/month available
4. Redirect dividends:             $X,XXX/quarter available
5. Deploy available cash:          $X,XXX available

After zero-tax moves:
  Remaining imbalance: $X,XXX to rebalance in taxable account

Step 3: Optimize Taxable Account Sales

For the remaining imbalance that requires selling in taxable:

For each overweight position in taxable:
  List all tax lots sorted by tax efficiency:
  
  Lot   Shares  Basis    Current  Gain/Loss  Type    Tax Cost
  1     100     $45.00   $80.00   $3,500     LT      $525
  2     50      $72.00   $80.00   $400       LT      $60
  3     75      $85.00   $80.00   ($375)     ST      -$131 (savings!)
  
  SELL ORDER: Lot 3 first (loss), Lot 2 next (small LT gain), Lot 1 last

Step 4: Calculate Total Rebalancing Tax Cost

REBALANCING TAX ANALYSIS

Option A: Naive Rebalance (sell proportionally)
  Sales Required:            $XX,XXX
  Realized Gains:            $XX,XXX
  Federal Tax:               $X,XXX
  State Tax:                 $X,XXX
  Total Tax Cost:            $X,XXX

Option B: Tax-Optimized Rebalance
  Zero-tax moves:            $XX,XXX rebalanced (no tax)
  Taxable sales (lot-optimized): $XX,XXX
  Realized Gains:            $XX,XXX
  Realized Losses:           ($X,XXX)
  Net Taxable:               $XX,XXX
  Federal Tax:               $X,XXX
  State Tax:                 $X,XXX
  Total Tax Cost:            $X,XXX

Option C: Phased Rebalance (over X months)
  Phase 1 (now):             Zero-tax moves + loss harvesting
  Phase 2 (contributions):   Direct $X,XXX/month to underweight
  Phase 3 (after lots go LT): Sell $XX,XXX in LT lots
  Total Tax Cost:            $X,XXX
  Timeline:                  X months to target

TAX SAVINGS: Option B saves $X,XXX vs Option A
             Option C saves $X,XXX vs Option A

Step 5: Generate Action Plan

RECOMMENDED REBALANCING PLAN

IMMEDIATE (this week):
□ Rebalance within 401(k): Sell $X of [Fund], Buy $X of [Fund]
□ Rebalance within IRA: Sell $X of [Fund], Buy $X of [Fund]
□ Sell [TICKER] Lot #3 (loss harvest): $X,XXX
□ Buy $X,XXX of [underweight fund] with proceeds

THIS MONTH:
□ Turn off DRIP on [overweight tickers]
□ Change 401(k) contributions to 100% [underweight fund]
□ Deploy $X,XXX cash to [underweight fund]

WITHIN 3 MONTHS:
□ Wait for [TICKER] lots to reach long-term status on [DATE]
□ Then sell $X,XXX of long-term lots
□ Buy $X,XXX of [target fund]

ONGOING:
□ Direct all new savings to [underweight asset class]
□ Review allocation quarterly
□ Target completion date: [DATE]

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Rebalancing Bands (When to Rebalance)

Help users set up rebalancing triggers:

Common Approach: Rebalance when any asset class drifts >5% from target

Target   Band         Rebalance Trigger
60%      55-65%       If stocks drop below 55% or exceed 65%
30%      25-35%       If bonds drop below 25% or exceed 35%
10%      5-15%        If intl drops below 5% or exceeds 15%

Tax-Aware Modification:
- Only rebalance using tax-free methods unless drift exceeds 10%
- Harvest losses opportunistically when they appear
- Use calendar-year boundaries strategically

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Special Scenarios

Major Allocation Change (e.g., 90/10 → 60/40)

When someone wants a large shift, a phased approach is almost always better:

• Phase over 6-12 months
• Prioritize selling losses and highest-basis lots
• Use new contributions aggressively
• Consider if the urgency justifies the tax cost

Concentrated Stock Position

When someone has too much in a single stock (e.g., employer stock):

• Sell in annual tranches to manage bracket impact
• Pair with loss harvesting in other positions
• Consider charitable giving of appreciated shares
• Look into exchange funds or protective puts (advanced)

Post-Retirement Rebalancing

Different considerations when in retirement:

• May be in lower tax bracket (more room for gains)
• Required Minimum Distributions (RMDs) force traditional IRA sales
• Use RMDs to rebalance (direct to underweight assets)
• Roth conversions can be combined with rebalancing strategy

Tax-Gain Harvesting

In low-income years (job loss, sabbatical, early retirement):

• Intentionally realize long-term gains while in 0% LTCG bracket
• Reset cost basis to higher level for free
• Opposite of tax-loss harvesting — equally valuable

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Important Disclaimers

• This analysis is for planning purposes; actual taxes depend on complete tax situation
• Tax lot information should be verified against brokerage statements
• Rebalancing involves investment risk — selling one asset to buy another exposes you to timing risk
• Wash sale rules apply when selling at a loss and buying similar securities within 30 days
• Consult a tax professional before making major portfolio changes

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Reference Data

Read references/tax-rates-2025.md for current tax rates. The capital-gains-estimator skill can be used for detailed gain/loss calculations on individual positions. The tax-loss-harvesting-tracker skill can identify loss harvesting opportunities as part of the rebalancing process.