MosoFin skill · credit-memo-and-refund-handler · learning guide

From one credit memo to the credits nobody uses

This page shows how the skill records money that goes back, one level at a time. It starts with one credit against one invoice. It ends with the items that the skill routes away or refuses. The page quotes every rule from the skill and works every number in front of you.

The rules are the skill's ownThe page quotes each rule word for word, with the file and section it comes from.

Outside sources back the factsThey are two sections of an OpenStax textbook, two HMRC pages, an ATO page, an FTC page and the IFRS 15 standard. Each one has a number and a link.

The page shows the mathOpen "Check it yourself" on any level. Follow every line on a calculator.

Your numbers, your checkAt the end, enter one credit and its original invoice. The page checks the tax, the limit and the draft entry.

Rule: quoted from the skill Fact: from a cited authority, numbered like ¹ Example: made-up figures, calculated in full

How it thinks

Nine rules the whole skill runs on

Every level below applies one or more of these rules. The examples use one made-up company, Northbrook Trading. Northbrook keeps its books in US dollars on the accrual basis and charges 7.5% sales tax on its sales. The skill runs on Wednesday 30 September 2026, through the owner's Mosofin connection, for the September 2026 period.

Learning path

Six levels, from simple to complex

Check it yourself

Check one credit

Enter one credit and its original invoice, or load an example. The page runs the limit check from Step 2, the tax check from Step 3 and the draft entry from Step 4 of references/method.md. The page sends nothing anywhere.

The original invoice Invoice net amount Tax rate, % Open balance before this credit Earlier credits to date, gross

This credit Type Credit net amount Tax on the credit (optional)

For a sales return Units back Unit cost Units damaged NRV for each damaged unit

The page calculates the expected tax as the credit net amount times the rate of the original, rounded to the cent. When a credit is more than the open balance, the rest goes on account. The page always credits Accounts Receivable, because a credit on account is a credit balance in receivables. For a goodwill credit, the page assumes that the credit has an original invoice. Without an original, the page cannot mirror the tax. NRV is net realizable value. You supply it, because the books cannot show that goods came back broken. To test the limit check, enter a net amount of 3,000, a rate of 7.5% and earlier credits of 1,075. Then enter an open balance of 2,150 and a credit net amount of 2,200. Credits to date of 3,440 are 215 more than the original 3,225.

Using it

What it asks, needs and gives back

Asks firstUse Mosofin for this run, or upload the data yourself? What type of credit is it, and for a chargeback, which kind? Which original invoice or bill? How much is the credit? What is the reason? Which tax jurisdiction? Which period? Who approves a credit that is more than the original?

NeedsThe skill needs the credit document and the original invoice or bill. It needs the type, the reason and the amount from you. It needs the chart of accounts, and the jurisdiction when the original had tax. The aging detail lets it list unapplied credits.

Gives backThe skill gives back six sheets: the credit register, draft entries, application tracking, unapplied credits, validation exceptions and coverage. It asks before it makes an Excel file.

NeverThe skill never reads your data before you answer its questions and say yes to its read-back. It never writes to any system, and it never guesses the reason, the type or the tax. It never proposes a second entry on application, and never proposes a refund on mock data.

Sources

Where every fact on this page comes from

The rules are the skill's own. The facts below come from seven outside sources. They are two sections of an OpenStax textbook, two HMRC pages, an ATO page, an FTC page and the IFRS 15 standard. MosoFin checked each one on 28 October 2026 from search results and did not open the pages. Follow the link for today's wording.

Not backed by an outside authority. The skill itself sets the list of eight credit types, the four Step 2 checks and the six sheets. It also puts vendor credits first. The 7.5% sales tax rate comes from an example in the skill. MosoFin made up Northbrook Trading, its customers, its suppliers and every figure in the examples. Northbrook is a US company, and each US state sets its own sales tax. So the page cites no US tax authority for the tax lines. The UK and Australian sources show the same idea in two other countries.