IHT400 Form: Complete Guide to Inheritance Tax Return UK 2025

The IHT400 is the full Inheritance Tax form required for estates over £325,000 (or £500K with Residence Nil-Rate Band). This comprehensive guide walks you through completing the IHT400 step-by-step, including required schedules, common mistakes, and submission to HMRC.

IHT400 vs IHT205: Which Form Do You Need?

Use IHT400 (full form) if estate:

• Over £325,000 (or £500K with RNRB)
• OR includes foreign assets over £100K
• OR includes trust property
• OR deceased made large gifts in last 7 years
• OR doesn't qualify as "excepted estate"

Use IHT205 (simple form) if ALL apply:

• Estate under £325K (£500K with RNRB)
• UK domiciled
• No trust assets
• No gifts over £3K/year in last 7 years
• Foreign assets under £100K

Before You Start: Documents Needed

Gather these before beginning the form:

• Death certificate
• Will (if there is one)
• Property valuations
• Bank statements (date of death balances)
• Investment valuations
• Pension statements
• Life insurance policy details
• Vehicle valuations
• Mortgage/debt statements
• Details of gifts in last 7 years

Create a spreadsheet listing all assets and debts - this becomes your reference.

Completing IHT400: Section by Section

Pages 1-3: About the Deceased

Basic information:

• Full name, date of birth, date of death
• National Insurance number
• Last address
• Marital status
• Domicile (UK for most people)
• Occupation

Pages 4-5: Executor Details

• Your name and address
• Contact details (phone, email)
• Relationship to deceased

Pages 6-8: UK Assets

List ALL UK assets with values at date of death:

• Property (use box IHT405)
• Bank accounts (use box numbers carefully)
• Savings and investments
• Personal belongings
• Vehicles

Critical: Use date of death values, not current values.

Pages 9-10: Debts and Liabilities

• Mortgage balance
• Loans and credit cards
• Funeral expenses
• Outstanding bills

Pages 11-12: Gifts and Transfers

List gifts made in 7 years before death:

• Gifts over £3,000 per year
• Transfers to trusts
• Gifts with reservation of benefit

Pages 13-15: Exemptions and Reliefs

• Spouse exemption (unlimited)
• Residence Nil-Rate Band (up to £175K)
• Business/agricultural relief
• Charitable gifts

Pages 16-18: Tax Calculation

Calculate tax:

1. Total assets minus debts = Net estate
2. Minus exemptions (spouse, charity)
3. Minus Nil Rate Band (£325K + RNRB)
4. = Taxable amount × 40% = Tax due

Pages 19-20: Declaration and Schedules

• List which schedules you're including
• Sign declaration (executor signature required)

IHT400 Schedules: Which Ones Do You Need?

Most common: IHT400 + IHT405 + IHT406 + IHT407 + IHT419 + IHT435

Common IHT400 Mistakes to Avoid

Submitting IHT400 to HMRC

Submission Methods

Online (recommended):

• Via HMRC Inheritance Tax online service
• Faster processing (1-3 weeks typically)
• Can track progress
• Still need to post supporting documents

Paper:

• Post to: HMRC Inheritance Tax, BX9 1HT
• Slower (3-6 weeks)
• No tracking
• Use recorded delivery

Include With Submission

• Completed IHT400 and schedules
• Copy of will
• Copy of death certificate
• Property valuations
• Bank letters confirming balances
• Investment valuations
• Evidence of debts

HMRC Processing and Queries

Typical timeline:

• Simple estates: 2-4 weeks
• Complex estates or queries: 6-12 weeks

HMRC may query:

• Property valuation seems low
• Missing gift information
• Unclear beneficiary shares
• Need additional evidence for reliefs

Response time: Usually 30 days - respond quickly to avoid delays

Paying Inheritance Tax

When it's due: 6 months after end of month of death

Must be paid BEFORE probate grant issued

Payment methods:

• Direct Payment Scheme from deceased's accounts
• Pay from own funds (reclaim from estate later)
• Installments for property (10 annual payments, interest charged)

After HMRC Clearance

Once HMRC is satisfied:

• Issues IHT reference number
• Confirms tax position
• Provides clearance to apply for probate

Use IHT400 with probate application - registry won't process without IHT clearance.

Getting Professional Help

Consider professional help if:

• Estate over £500K
• Business assets
• Foreign property/assets
• Complex gifts
• Unsure about any section

Typical costs: £1,500-5,000 (deductible from estate)