What it means
Financial contracts promise payments on specific dates. Calendars do not cooperate: a payment date can land on a weekend, a bank holiday, or a day when one country's banks are open and the other's are shut.
Date-rolling conventions exist to solve this mechanically, so nobody renegotiates a swap because of a public holiday. The simple conventions roll following, to the next business day, or preceding, to the one before.
Modified following adds a guardrail. Rolling forward across a month-end would move a payment into a different month, changing accrual periods and sometimes valuation, so the convention rolls back to the last business day of the original month instead.
The rule matters most in derivatives. Swap confirmations specify a business day convention for every date, and the standard definitions published by the International Swaps and Derivatives Association define modified following exactly as roll forward unless the result falls in the next calendar month.
Accrual arithmetic explains the preference. Interest for a period is counted in days within the month, and a payment drifting into the next month stretches or squeezes that count in ways both sides must then reconcile.
Choosing the convention is a commercial detail with cash consequences. Modified following keeps payments inside their intended month, which is why it is the common choice for payment dates in interest rate and currency swaps.
For a business owner, the convention hides inside loan and hedging documents. A treasurer comparing two swap quotes should check that both use the same date conventions, because a payment rolling into a different month can quietly shift cash flow and interest accruals.
In practice
Real-world examples.
Example
A swap payment dated for the last day of May falls on a Sunday. Rolling forward lands on the first of June, a new month, so modified following moves the payment back to the preceding Friday in May.
Example
A loan between a London borrower and a Gulf bank specifies modified following for every payment date. A date falling on a holiday observed in only one centre adjusts mechanically, with no phone call required.
Example
A treasurer audits a hedge and finds one confirmation uses following while its twin uses modified following. The mismatch shifts a year-end payment into January, and she has it corrected before it distorts the accounts.
Formula
Calculation
Date adjustment rule: adjusted date = next business day after the stated date, unless that day falls in the following calendar month, in which case adjusted date = the last business day of the stated month. A payment due Sunday the 31st adjusts to Friday the 29th, never to Monday the 1st.
Worked example: a swap payment is due on Saturday the 30th of a 30-day month. The next business day is Monday the 2nd of the following month, which crosses the month-end, so modified following moves the payment back to Friday the 29th. If the payment were due on Saturday the 10th instead, the next business day is Monday the 12th, in the same month, so the payment rolls forward. For a $5,000,000 notional at 6% a year on a 360-day basis, one day of interest is $5,000,000 x 6% / 360 = about $833.33, so a three-day shift into the next month would move about $2,500 of interest between periods.Case study
Seen in the real world.
In this illustrative fictional case, Priya, treasurer of an import business, hedges a dollar loan with an interest rate swap. The first payment date, set for month-end, falls during a holiday weekend. Because the confirmation specifies modified following, the payment settles the Friday before, inside the same month, matching her interest accrual exactly. Her counterpart, hedged under plain following on a separate deal, pays three days later in the next month and spends an afternoon explaining the mismatch to his auditors. Priya files the lesson: in derivatives, the smallest defined terms carry real cash.
Watch out
Common mistakes.
- Assuming dates adjust the same way in every contract, when following, modified following and preceding are different conventions chosen per confirmation.
- Ignoring the month-crossing rule, when rolling forward across a month-end changes accrual periods and can shift cash between accounting periods.
- Forgetting that holidays differ by centre, when a date good in one country may be a bank holiday in the other, which is exactly what the convention exists to resolve.
Questions
People also ask.
What is the difference between following and modified following?
Following rolls a date to the next business day regardless. Modified following does the same unless the result crosses into the next calendar month, in which case it rolls back to the previous business day.
Where is modified following used?
Mainly in derivatives and loan documentation. Swap confirmations specify a business day convention for each date, and modified following is common for payment dates to keep them in their intended month. ISDA's standard definitions supply the exact wording most swap documentation adopts.
Why not always roll forward?
Rolling forward across a month-end moves the payment into a different month, altering accruals and sometimes valuations. The modification preserves the original month, which is usually what both parties intended.
From the founder's library
Take it further with the book.
Build your financial confidence beyond this definition. Shihan's full-length guide, Accounting Fundamentals, takes the same plain-English approach and turns it into a complete, practical playbook for non-finance managers, business owners and students - with chapter-end quiz answers and presentation slides included.
25% off with code MMHQ25, applied at checkout. Priced in USD - checkout may show the equivalent in your local currency.
View the book and save 25%