Here is a comprehensive list of considerations: 

1. Capital Gains Tax: 

Calculate capital gains: Deduct the cost of acquisition/improvement and the cost of sale from the sale proceeds. 

Determine whether the gains are short-term (held for less than 2 years) or long-term (held for more than 2 years). 

2. Types of Capital Gains: 

Short-Term Capital Gains (STCG): Taxed at applicable slab rates. 

Long-Term Capital Gains (LTCG): Taxed at 20% with indexation or 10% without indexation, whichever is lower. 

3. TDS (Tax Deducted at Source): 

The buyer is required to deduct TDS at the rate of 20% on the capital gains before making the payment to the NRI seller. 

4. Tax Exemptions and Deductions: 

Exemptions under Section 54 (for reinvesting in another property) or Section 54EC (investment in specified bonds) can be availed to save on capital gains tax. 

5. Compliance under FEMA (Foreign Exchange Management Act): 

File Form 15CA and 15CB: NRI sellers need to submit Form 15CA and obtain Form 15CB from a chartered accountant for remittance of sale proceeds. 

6. Repatriation of Sale Proceeds: 

NRIs can repatriate up to USD 1 million per financial year for the sale of immovable property in India, after paying applicable taxes. 

7. Bank Account: 

Maintain an NRO (Non-Resident Ordinary) account for receiving sale proceeds. Funds in NRO accounts are repatriable up to a limit. 

8. Tax on Rental Income: 

If the property was generating rental income, TDS provisions and tax on rental income need to be considered. 

9. Compliance with Local Authorities: 

Fulfill any local authority requirements for property sale and transfer. 

10. PAN (Permanent Account Number): 

Ensure that the NRI seller has a PAN in India as it is required for TDS purposes. 

11. Certificate of Ownership: 

Obtain a certificate of ownership and encumbrance to establish clear title during the sale. 

12. Capital Gains Account Scheme (CGAS): 

If the NRI seller is not buying another property immediately, funds can be deposited in a CGAS account to avail of tax exemptions later. 

13. Consultation with Tax Advisor: 

Seek advice from a tax consultant or chartered accountant to navigate the complexities of tax laws and compliance. 

14. Exit Tax on Unlisted Shares and Units: 

If the property is held through an unlisted company or unit, the provisions of exit tax under Section 115QA may apply. 

It's crucial to note that tax laws are subject to change. It is highly recommended to consult with a tax professional for the most current and personalized advice tailored to your client's specific situation.