Contract Payment Calculator

Overview

A payment clause in a contract usually carries four things at once: the tax-inclusive contract value, a deposit percentage, a number of instalments and a late-payment penalty. The step that quietly breaks manual schedules is the rounding tail. Splitting the remaining balance into three equal parts rarely divides cleanly at the cent, and if the last instalment does not absorb the leftover the schedule will not add up to the contract value. This calculator first splits the contract value into net and tax, computes the deposit from the chosen percentage, spreads the remainder across the instalments and lets the final one absorb the difference, then applies the daily penalty rate to the overdue days. The daily rate is entered as a percentage, so five basis points per day is written as 0.05, and the output includes both the total receivable and a payment schedule table that can be exported.

Features

• Contract value accepted as tax-inclusive or exclusive, split into net and tax at 13, 9, 6, 3 or 0 percent
• Deposit and instalment schedule generated automatically, with the final payment absorbing the rounding difference
• Late fee computed as contract total times daily rate times overdue days, so five basis points per day is 0.05
• Eight outputs at once: net value, tax, gross, deposit, instalment amount, final payment, penalty and total receivable
• The schedule lists deposit, each instalment and the final payment so it can be checked against the payment plan
• Copy the four key numbers or export the schedule as CSV for the receivables ledger

How to use

1. Enter the contract total and mark whether it already includes tax
2. Select the contract tax rate and confirm the net amount and tax after the split
3. Fill in the deposit percentage as a number such as 30, and the number of instalments as a whole number
4. Enter overdue days and the daily penalty rate, writing 0.05 for five basis points; use zero days when nothing is overdue
5. Read the total receivable and the schedule, then copy the figures or export CSV into the ledger

Notes

• The rounding tail lands on the last instalment: each payment is truncated to the cent and the remainder is added back at the end so the schedule reconciles
• The penalty base defaults to the tax-inclusive total; if the contract charges interest on the unpaid portion only, put the unpaid amount into the contract field instead
• The daily rate is read as a percentage, so 0.05 means five basis points a day and roughly 18.25 percent a year; clauses above the statutory cap risk being reduced
• The deposit percentage applies to the inclusive total by default; if the contract pays a deposit on the net value, switch the basis first
• This tool does not capitalise interest or compound it; a long overdue balance split into periods needs one calculation per period
• The schedule ignores invoicing and acceptance gates, which in practice still condition when money is actually due
• Penalty figures are a computation aid and should be reconciled against the governing contract terms before invoicing
• Each instalment is floored to the cent and the final one absorbs the remainder, so the schedule always adds back to the contract total exactly; the penalty line is informational and is not merged into the receivable sum.