Question: My Father bought 20 year life insurance savings policy with sum assured of Rs 12,00,000. He paid all the annual premiums regularly for 8 years but then stopped paying further premiums due to financial difficulties. The insurer informed him that the policy would continue as reduced paid up policy instead of lapsing. Before the policy became paid up the policy had already accumulated vested bonuses of Rs 1,50,000. When the policy completes its full 20 year term, how much total maturity benefit will be payable under the reduced paid up option?
Answer: Since only 8 out of the 20 required premiums were paid, the policy will continue with a reduced paid up value instead of full sum assured.
Paid up factor = 8 / 20 = 40%
Reduced Paid up Sum Assured = Rs 12,00,000 * 40% = Rs 4,80,000
The policy had already accumulated vested bonuses of Rs 1,50,000 before it became paid up. These vested bonuses remain attached to the policy and are added to the reduced paid up sum assured at maturity.
Total Maturity Benefit = Rs 4,80,000 + Rs 1,50,000 = Rs 6,30,000
Therefore, the total amount payable at maturity under the Reduced Paid up policy will be  Rs 6,30,000.

Supporting evidence:
title: old.irdai.gov.in/110N029V02.pdf
quote: Reduced Paid up Sum Assured = (No. of Premiums paid) / (Nos. of Premium payable, during the entire Policy term) x Basic Sum Assured Minimum Guaranteed Sum Assured on maturity x (No of premiums paid)/ (No of premiums payable, during the entire policy term) shall be payable
context: ovided at least the first full years' premium has been paid. The surrender value payable is higher of Guaranteed Surrender Value or Special Surrender Value

a) Guaranteed Surrender Value (GSV)

Guaranteed Surrender Value = (Total Premiums Paid x Guaranteed Surrender Value factor) - Total Guaranteed Annual Coupons already paid, if any
Guaranteed surrender value factor will be as per table annexed as Annexure - A with this Contract.

b) Special Surrender Value (SSV)

Special Surrender Value = Special Surrender Value Factor x Reduced Paid up Sum Assured
Reduced Paid up Sum Assured = (No. of Premiums paid) / (Nos. of Premium payable, during the entire Policy term) x Basic Sum Assured.
Special Surrender value factor will vary according to the Age of Life Insured and Policy Year of Surrender and as per table annexed as Annexure - A with this Contract.
We have the right to review the basis for calculating the SSV factors from time to time based on the experience and any change thereto shall be subject to prior approval of Insurance Regulatory and Development Authority of India.

2. Reduced Paid-Up:

If the full premium for atleast the first policy year has been paid, and subsequent premiums remain unpaid, the Policy will be converted into a Reduced Paid Up Policy by default. Once the policy becomes reduced paid up, the policy shall not be entitled to any further Non guaranteed Cash dividends.
In case of Reduced paid up policies, the benefit shall be payable as under :
- a. Death Benefit : On death of the Life Insured during the policy term, Sum Assured on death x (No of premiums paid)/ (No of premiums payable, during the entire policy term) shall be paybale.
This total amount will be subject to a minimum of 105% of Total Premiums Paid, as on the date of death

b. Maturity Benefit :

Minimum Guaranteed Sum Assured on maturity x (No of premiums paid)/ (No of premiums payable, during the entire policy term) shall be payable
The Guaranteed Annual coupons, calculated on Reduced Paid up Sum Assured will also be payable along with the above maturity benefit.

c. Survival Benefit

Guaranteed Annual Copuons shall be payable, at the rate as mentioned in B (2) (a) of this Contract on Reduced Paid up Sum Assured on every Policy Anniversary, commencing from 10 th Policy Anniversary till maturity or till death whichever is earlier.
Reduced Paid up Sum Assured = (No. of Premiums paid) / (Nos. of Premium payable, during the entire Policy term) x Basic Sum Assured.