How should I practice Transaction Fee Calculator - Status Gate and Regional Rates?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Stripe phone screen problems in FastPrep.

Is Transaction Fee Calculator - Status Gate and Regional Rates associated with Stripe?

FastPrep tags this as a Stripe phone screen coding practice problem when the problem catalog has that company and stage context.

Problem · String

Transaction Fee Calculator - Status Gate and Regional Rates

Learn this problem

● Easy

StripeFULLTIMEPHONE SCREEN

See Stripe hiring insights

Problem statement

Compute the processing fee for each transaction in a CSV and emit a result CSV.

Input: csvData is a single CSV string. The first row is the header; the canonical columns are id,reference,amount,currency,date,merchant_id,buyer_country,transaction_type,payment_provider,status. amount is an integer in cents. payment_provider is one of card, klarna, bank_transfer. status is one of payment_completed, payment_failed, payment_pending.

Fee rules: the fee for a row is floor(amount * rate + fixed) using these rates by (buyer_country, payment_provider):

Standard (any country except Ireland): card = 2.9% + 30, klarna = 3.5% + 50, bank_transfer = 0.8% + 0.
Ireland (buyer_country == "ie"): card = 1.9% + 20, klarna = 2.5% + 40, bank_transfer = 0.6% + 0. Any other country falls back to the standard rates.

A fee is only charged when status == "payment_completed"; for failed or pending transactions the fee is 0. Always floor the final fee to an integer (truncate toward zero).

Output: return a String[] whose first element is the header "id,transaction_type,payment_provider,fee" and then one line "id,transaction_type,payment_provider,fee" per input transaction, in input order.

Function

calculateFees(csvData: String) → String[]

Examples

Example 1

csvData = "id,reference,amount,currency,date,merchant_id,buyer_country,transaction_type,payment_provider,status\npy_1,ref1,1000,eur,2026-01-01,m1,ie,payment,card,payment_completed\npy_2,ref2,2500,eur,2026-01-01,m1,ie,payment,card,payment_failed\npy_3,ref3,3400,eur,2026-01-01,m2,ie,payment,klarna,payment_completed\npy_4,ref4,5000,eur,2026-01-01,m2,fr,payment,bank_transfer,payment_completed\npy_5,ref5,2000,eur,2026-01-01,m3,ie,payment,card,payment_pending"return = ["id,transaction_type,payment_provider,fee", "py_1,payment,card,39", "py_2,payment,card,0", "py_3,payment,klarna,125", "py_4,payment,bank_transfer,40", "py_5,payment,card,0"]

py_1: Ireland card, completed -> 1000*0.019 + 20 = 39. py_2: failed -> 0. py_3: Ireland klarna, completed -> 3400*0.025 + 40 = 125. py_4: France falls back to the standard bank_transfer rate -> 5000*0.008 + 0 = 40. py_5: pending -> 0.

Example 2

csvData = "id,reference,amount,currency,date,merchant_id,buyer_country,transaction_type,payment_provider,status\npy_1,ref1,1000,usd,2026-01-01,m1,us,payment,card,payment_completed\npy_2,ref2,2500,usd,2026-01-01,m1,us,payment,card,payment_completed\npy_3,ref3,3400,usd,2026-01-01,m2,us,payment,klarna,payment_completed\npy_4,ref4,5000,usd,2026-01-01,m2,us,payment,bank_transfer,payment_completed"return = ["id,transaction_type,payment_provider,fee", "py_1,payment,card,59", "py_2,payment,card,102", "py_3,payment,klarna,169", "py_4,payment,bank_transfer,40"]

All US (standard rates), all completed. py_1: 1000*0.029 + 30 = 59. py_2: 2500*0.029 + 30 = 102.5 floored to 102. py_3: 3400*0.035 + 50 = 169. py_4: 5000*0.008 + 0 = 40. (This reproduces the page's Part-1 standard-rate example.)

Constraints

First CSV row is the header; amount is integer cents.
Fee = floor(amount * rate + fixed) by (buyer_country, payment_provider); Ireland has its own rates, all other countries use the standard rates.
Fee is 0 unless status == "payment_completed".
Floor (truncate) the final fee to an integer.
Return a String[]: header "id,transaction_type,payment_provider,fee" then one line per transaction in input order.