How to Track Interest on Loans Given to Friends, Family or Customers (India 2026)
If you've ever lent money to a friend, family member, or a customer "with interest," you know the awkward part isn't lending — it's keeping accurate records and following up. This guide shows the formulas, the common pitfalls, and the easiest digital workflow using VyajPay.
Step 1 — Pick the right interest model
Simple interest (sadharan vyaj)
SI = (P × R × T) / 100
Best for short, single-shot loans (e.g. ₹50,000 for 6 months at 12% per year). Easy to compute, easy to explain to the borrower.
Compound interest (chakravriddhi vyaj)
A = P × (1 + R/100)^T
Used when interest is added back to principal each period (monthly/quarterly/yearly). Earns more for the lender on long-tenure loans.
Flat-rate EMI
Total interest is computed on the original principal across the full tenure, then divided equally with principal across all EMIs. Common with informal lenders. Effective rate is roughly 1.8× the quoted rate.
Reducing-balance EMI
EMI = [P × r × (1+r)^n] / [(1+r)^n − 1]
The bank standard. Interest is recalculated each month on the outstanding balance. Fairer to the borrower; more work to compute manually.
Step 2 — Decide what to record
For every loan, capture at minimum:
- Borrower name, phone, and address
- KYC reference (Aadhaar/PAN) and a witness if it's a large loan
- Principal amount and date disbursed
- Interest rate and computation method
- Tenure and EMI schedule
- Each repayment with date and mode (cash/UPI/bank)
- A signed acknowledgement (a simple loan note works)
Step 3 — Pick a tracking method
Notebook (paper khata)
Pros: No tech. Cons: Lost on rain, ink fades, math errors, no reminders, no proof if disputed.
Excel template
Pros: Free. Cons: Requires you to maintain formulas, no automated reminders, only one device, easy to corrupt.
Generic khata app (Khatabook / OkCredit)
Pros: Mobile-first, free. Cons: Built for retail udhaar — no proper EMI scheduling or reducing-balance interest.
Lender-specific app (VyajPay)
Pros: All of the above plus auto EMI schedule, automated WhatsApp/SMS reminders, PDF statements, web dashboard. Cons: ₹200/month for Pro features.
Step 4 — Use VyajPay (15-minute setup)
- Add the borrower with name, phone, photo, and KYC.
- Create the loan — enter principal, interest rate, tenure, and pick flat or reducing.
- Confirm the EMI schedule the app generates.
- Enable WhatsApp reminders so you never have to call.
- Record payments as they come in (full or partial).
- Share the PDF statement with the borrower whenever they ask.
Common mistakes Indian lenders make
- Using simple interest formula but quoting the rate as if it were reducing-balance — borrowers feel cheated when they realise.
- No written acknowledgement — making recovery harder if disputed.
- Not adjusting partial payments correctly to principal vs interest.
- Tracking everything in head — leading to "ghost loans" forgotten over years.
- Ignoring the state's Money Lenders Act registration if lending is a business.
If lending is your livelihood, register under your state's Money Lenders Act and respect the prescribed maximum interest rate. Personal occasional loans to family typically don't require a license, but always check.
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Download VyajPay (Android) Try Free SI CalculatorFAQ
What is the simple interest formula?
SI = (P × R × T) / 100
What is the EMI formula?
EMI = [P × r × (1+r)^n] / [(1+r)^n − 1], where r is the monthly interest rate.
Is it legal to lend money with interest in India?
Yes, but lending as a business typically requires registration under your state's Money Lenders Act and compliance with rate caps.