Various Adjustments of Tax Numbers for 2021

Filing statuses: S=single, HH=head of household, MFS=married filing separately, MFJ=married filing joint, QW=qualifying widow(er);
(MAGI mean modified adjusted gross income for that deduction)

The Tax Cut and Jobs Act (TCJA) is in effect 2018 through 2025, unless modified or extended in the future. Changes to various tax deductions are indicated below.
Maximum Salary Deferrals: $19,500 for 401(k), 403(b), 501(c), 457 plans; / $13,500 for SIMPLE
'catch-up'contribution limits for age 50+: (additional $6,500 / $3,000 for SIMPLE)
$2,750 for Health FSA
Self-Employed: SEP-IRA: $58,000, with limitation of 20% adjusted net s/e income
Traditional IRA Contributions Limit: $6,000 (up to amount of earned income for the year)
  additional catch-up $1,000 for age 50+

Traditional IRA Deduction MAGI Phaseout:
(when also eligible to contribute
to a retirement plan at work)
MFJ, QW:  $105,000-$125,000
S, HH:  $66,000-$76,000
MFS:  0-$10,000 (living apart all year, see S)
MFJ taxpayer when only other spouse covered by a plan: $198,000-$208,000

Roth IRA Contributions MAGI Phaseout:
MFJ:  $198,000-$208,000
S, HH:  $125,000-$140,000
MFS:  0-$10,000 (living apart all year, see S)

Retirement Savings Credit ('Saver's Credit')
Maximum AGI Limit:
MFJ:  $66,000
HH:  $49,500
S, QW, MFS:  $33,000
Social Security: Before retirement age, can earn up to $18,960 without repaying benefits.
  Benefits reduced $1 for each $2 earned over limit
Preceding months in year of reaching retirement age: $50,520.
  Benefits reduced $1 for each $3 earned over limit
On/after retirement month, no limit.
Maximum monthly benefits for 2021: $3,895

Earnings subject to SS tax:
  Employee: $142,800 (maximum $8,854 w/h)
  Household help: cash wages over $2,300
Health Savings Account: Maximum HSA contribution $3,600 individual coverage / $7,200 family coverage.
  additional catch-up $1,000 for age 55+
Child Tax Credit: increases to $3,600 per child under 6, $3,000 age 6 through 17,
  with phaseout starting at a higher AGI level of 400K MFJ, 200K others.
$500 credit for other dependents.
(TCJA and American Rescue Plan)
Child Care Expenses/Credit: Allowed expenses for credit increases from 3K one child (6K two or more) to 8K/16K.
  Dependent care benefits set-aside increases from $5K to $10.5K.
  Maximum credit $4K /$8K (one child / two or more children)
(American Rescue Plan, 2021 only)
Educational Credit:  (MFS ineligible) American Opportunity Credit (aka Hope Credit):
100% of first $2,000, 25% of next $2,000 tuition (all 4 years college)
   MAGI phaseout: $80,000-$90,000 (individual); $160,000-$180,000 (MFJ)
Lifetime Learning Credit: 20% of up to $10,000 tuition (any year college+)
   MAGI phaseout: $59,000-$69,000 (individual); $118,000-$138,000 (MFJ)
Student Loan Interest:  (MFS ineligible) Up to $2,500
MAGI phaseout: $70,000-$85,000 (individual); $140,000-$170,000 (MFJ)
same as 2019.

Earned Income Credit:  (MFS ineligible)
Maximum Earned income/MAGI limit:
$21,430 (no children), $42,158 (one child), $47,915 (two children), $51,464 (three children)
 limits increased by $5,950 if MFJ
Maximum credit will range from $1,502 for no children up to $6,728 for three or more children.
(disqualified if investment income over $10,000, any filing status)
(American Rescue Plan):
  May calculated using 2019 earned income if it was higher than 2021 for more credit.
  EIC for taxpayer/no children temporarily increased for 2021, w/no upper age limit.
Adoption Credit: Up to $14,400 (phaseout $216,660-$256,660)
'Kiddie Tax': Child under 18/full-time student under 24, with interest/dividends over $2,200
'Secure Act' reversed TCJA which changed tax rates from parents' marginal rate from trust/estate tax brackets.
Standard Mileage Rates:   Business:  56¢  (Depreciation adjustment: 26¢)
  Charity:  14¢
  Medical:  16¢
Employee business expenses and nonmilitary moving expenses were eliminated (TCJA).
Itemized Deduction phaseout: This has been eliminated. And with no personal exemptions, that phaseout also eliminated. (TCJA).
Section 179 Expense: total limit for tangible personal property placed in service: $1,050,000
phaseout starts at $2.62M placed in service
Depreciation Limit (with/without bonus depreciation): Passenger auto limit, first year business: $10,200 / $18,200
Capital Gain Tax: Long-term (holding over a year):

0% for taxable income under $40.4K (S,MFS), $54.1K (HH), $80.8K (MFJ, QW)
15% for taxable income under $445,850 (S), $473,450 (HH), $501,600 (MFJ, QW) or $250,800 (MFS)
20% for taxable income over those amounts.
Gift Tax Exclusion/ Estate Exclusion: $15,000 / $11.7 M
Foreign Income Exclusion: $107,600